U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2016–5109

Prepared in cooperation with Natural Resources Canada, the International Joint 

Commission, and the National Park Service

Network Global Navigation Satellite System Survey to 

Harmonize Water-Surface Elevation Data for the Rainy 

River Basin
Front cover photograph: Namakan Lake near International Falls, Minnesota.

Back cover photograph: Rainy Lake near International Falls, Minnesota. 
Network Global Navigation Satellite 

System Survey to Harmonize WaterSurface Elevation Data for the Rainy River 

Basin

By Jeffrey R. Ziegeweid, R. Jason Silliker, Brenda K. Densmore, and 

Justin Krahulik

Prepared in cooperation with Natural Resources Canada, the International Joint 

Commission, and the National Park Service

Scientific Investigations Report 2016–5109

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

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Suggested citation:

Ziegeweid, J.R., Silliker, R.J., Densmore, B.K., and Krahulik, Justin, 2016, Network Global Navigation Satellite System 

survey to harmonize water-surface elevation data for the Rainy River Basin: U.S. Geological Survey Scientific Investigations Report 2016–5109, 20 p., http://dx.doi.org/10.3133/sir20165109.

ISSN 2328-0328 (online)
iii

Acknowledgments

Gail Faveri (Environment Canada) helped coordinate the joint field efforts between the United 

States and Canada, as well as the joint funding through the United States and Canadian offices 

of the International Joint Commission. Ryan Maki and Chuck Remus (Voyageurs National Park) 

coordinated the support of the National Park Service and logistical support to complete the field 

data collection. Jaime LeDuc and Claire Kissane (Voyageurs National Park) led a field crew to 

remote areas of Voyageurs National Park. Michael Craymer (Natural Resources Canada), Marc 

Véronneau (Natural Resources Canada), Jean Morin (Environment Canada), and Aaron Thompson (Environment Canada) provided input to improve the design of the survey and the presentation of the study results. Drs. Mark Colosimo and Wayne Jenkinson (International Joint Commission) approved the study and participated in regular progress reviews. Bill Odell (U.S. Army 

Corps of Engineers) provided reference mark and elevation data for the streamgage on Crane 

Lake. James Wilcox (Environment Canada) participated in field collection efforts and qualityassurance checks of collected data. Mark Schenewerk (National Oceanic and Atmospheric 

Administration) reviewed the report.

Chris Sanocki and Catherine Christenson of the U.S. Geological Survey participated in field data 

collection efforts. Scott Adolphson of the U.S. Geological Survey created the study area maps. 

Dave Lorenz (retired) and Jared Trost of the U.S. Geological Survey helped create and format 

report figures. Adam Mosbrucker of the U.S. Geological Survey reviewed the report. 
iv

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................4

Physical Setting.....................................................................................................................................4

Methods...........................................................................................................................................................6

Field Data Collection.............................................................................................................................6

Data Processing....................................................................................................................................6

Development of Streamgage Datum Offsets....................................................................................7

Application of Streamgage Datum Offsets.......................................................................................7

Global Navigation Satellite System Surveys.............................................................................................8

Survey Comparisons....................................................................................................................................10

Namakan Reservoir............................................................................................................................10

Rainy Lake............................................................................................................................................10

Rivers 10

2012 Namakan Reservoir Data .........................................................................................................10

Limitations of the Study...............................................................................................................................13

Summary........................................................................................................................................................16

References Cited..........................................................................................................................................16

Appendixes 1–3............................................................................................................................................19

Appendix 1. Global Navigation Satellite System Data Collection Information ........................20

Appendix 2. Processing of Raw Data Collected for 16 Atreamgage Reference Marks 

and 1 National Geodetic Survey Cooperative Base Network Control Station 

Using Global Navigation Satellite Systems.......................................................................20

Appendix 3. Surveyor Level Loop Information for Selected Sites ..............................................20

Figures

1. Maps showing water-level streamgage locations for Rainy Lake, Namakan 

Reservoir, and selected rivers....................................................................................................2

2. Map showing locations of the National Geodetic Survey cooperative base 

network control station, Canadian Active Control Stations, and Continuously 

Operating Reference Stations used to postprocess data collected from global 

navigation satellite system receivers in this study .................................................................5

3. Graph showing water-surface elevation data referenced to the Canadian 

Geodetic Vertical Datum of 2013 for the data collection period at active 

streamgages in Namakan Reservoir, which are identified using map and 

station numbers associated with data in table 1...................................................................11

4. Graph showing water-surface elevation data referenced to the Canadian 

Geodetic Vertical Datum of 2013 for the data collection period at active 

streamgages in Rainy Lake, which are identified using map and station 

numbers associated with data in table 1................................................................................12
v

5. Graph showing mean water-surface elevations referenced to the Canadian 

Geodetic Vertical Datum of 2013 for the data collection period at active 

streamgages on the Vermilion, Turtle, and Rainy Rivers; streamgages are 

identified using map and station numbers associated with data in table 1......................13

6. Graph showing monthly water-surface elevation data for all active and 

discontinued streamgages in Namakan Reservoir during the open water 

period of 2012, converted from streamgage datums to the Canadian Geodetic 

Vertical Datum of 2013 using offsets presented in table 4; streamgages are

identified using map numbers associated with data in table 1...........................................14

7. Graph showing published mean daily water-surface elevations for discontinued 

U.S. Geological Survey water-level streamgages on Sand Point Lake above and 

below Harrison Narrows in 2012..............................................................................................15

Tables

1. Information about streamgages in Rainy Lake, Namakan Reservoir, and selected 

rivers in Minnesota, Unites States, and Ontario, Canada......................................................3

2. Location information for the National Geodetic Survey cooperative base network 

control station, Canadian Active Control Stations, and Continuously Operating 

Reference Stations used to postprocess data collected from global navigation 

satellite system receivers in this study.....................................................................................4

3. Global Navigation Satellite System survey results for 16 streamgage reference 

marks and National Geodetic Survey cooperative base network control station 

AC4984, processed using Natural Resources Canada and U.S. Geological Survey 

methods..........................................................................................................................................8

4. Offsets to convert published water levels to water-surface elevations referenced 

to the Canadian Geodetic Vertical Datum of 2013 for streamgages in Rainy Lake, 

Namakan Reservoir, and selected rivers..................................................................................9

Appendix Table

1–1. Summary of collected satellite data for 16 streamgage reference marks and 

1 National Geodetic Survey cooperative base network control station surveyed 

in this study..................................................................................................................................20
vi

Conversion Factors

[International System of Units to U.S. customary units]

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft)

[U.S. customary units to International System of Units]

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

Datum

Vertical coordinate information is referenced to the Canadian Geodetic Vertical Datum of 2013 

(CGVD2013) or North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83) 

or Canadian Gravimetric Geoid of 2013 (CGG2013).

Elevation, as used in this report, refers to distance above the vertical datum.

Abbreviations

BSW Bernese GNSS Software v5.2

CACS Canadian Active Control System

CORS Continuously-Operating Reference Station

CSRS Canadian Spatial Reference System

EC Environment Canada

GLONASS Global Orbiting Navigation Satellite System 

(Russian)

GNSS Global Navigation Satellite System

IJC International Joint Commission

NGS National Geodetic Survey

NRCan Natural Resources Canada

OPUS Online Positioning Users Service

USACE U.S. Army Corps of Engineers

USGS U.S. Geological Survey
Network Global Navigation Satellite System Survey to 

Harmonize Water-Surface Elevation Data for the Rainy 

River Basin

By Jeffrey R. Ziegeweid,1 R. Jason Silliker,2 Brenda K. Densmore,1 and Justin Krahulik1

1

U.S. Geological Survey.

2

Natural Resources Canada.

Abstract

Continuously recording water-level streamgages in Rainy 

Lake and Namakan Reservoir are used to regulate water levels 

according to rule curves established in 2000 by the International Joint Commission; however, water levels at streamgages 

were referenced to a variety of vertical datums, confounding 

efforts to model the flow of water through the system, regulate water levels during periods of high inflow, and evaluate 

the effectiveness of the rule curves. In October 2014, the 

U.S. Geological Survey, Natural Resources Canada, International Joint Commission, and National Park Service began a 

joint field study with the goal of obtaining precise elevations 

referenced to a uniform vertical datum for all reference marks 

used to set water levels at streamgages throughout Rainy Lake 

and Namakan Reservoir. This report was prepared by the U.S. 

Geological Survey in cooperation with Natural Resources 

Canada, International Joint Commission, and National Park 

Service.

Three field crews deployed Global Navigation Satellite 

System receivers statically over 16 reference marks colocated with active and discontinued water-level streamgages 

throughout Rainy River, Rainy Lake, Namakan Reservoir, 

and select tributaries of Rainy Lake and Namakan Reservoir. A Global Navigation Satellite System receiver also was 

deployed statically over a National Geodetic Survey cooperative base network control station for use as a quality-control 

reference mark. Satellite data were collected simultaneously 

during a 5-day period and processed independently by the 

U.S. Geological Survey and Natural Resources Canada to 

obtain accurate positioning and elevations for the 17 surveyed 

reference marks. Processed satellite data were used to convert 

published water levels to elevations above sea level referenced 

to the Canadian Geodetic Vertical Datum of 2013 in order 

to compare water-surface elevations referenced to a uniform 

vertical datum throughout the study area. In this report, an 

“offset” refers to the correction applied to published data from 

a particular streamgage to produce elevation data referenced to 

a specified vertical datum.

Offsets were applied to water-level data from surveyed 

streamgages to further evaluate the accuracy and utility of 

updated reference mark elevations presented in this report. 

Daily mean water levels from active streamgages surveyed 

in this study were converted to water-surface elevations 

referenced to the Canadian Geodetic Vertical Datum of 

2013. Graphical comparisons of water-surface elevations for 

streamgages in Namakan Reservoir, Rainy Lake, and selected 

rivers are presented (referencing the Canadian Geodetic 

Vertical Datum of 2013). Offsets presented in this report can 

be used in the evaluation of rule curves and in flood damage 

curves that fully assess the benefits of one regulation approach 

over another. In addition, offsets may be used to calibrate 

hydraulic models developed for four narrows that connect 

lakes of Namakan Reservoir, refine digital elevation models, 

and support modeling studies designed to assess the effects 

of rule curves on aquatic vegetation, benthic invertebrates, 

northern pike, and walleye.

Introduction

The Rainy River Basin of northern Minnesota and 

southwestern Ontario is a complex system of lakes and rivers 

(Kallemeyn and others, 2003), including Namakan Reservoir, 

Rainy Lake, and several rivers that feed these lake systems 

(fig. 1). Namakan Reservoir includes Crane, Little Vermilion, 

Sand Point, Kabetogama, and Namakan Lakes. Rainy Lake 

drains into the Rainy River near the towns of Fort Frances, 

Ontario, and International Falls, Minnesota. Rainy River, 

the southern basin of Rainy Lake, and Namakan Reservoir 

form the international border between the United States and 

Canada.

Water levels in Rainy Lake and Namakan Reservoir are 

managed according to rule curves established by the International Joint Commission (IJC) with the assistance of the 

International Rainy Lake Board of Control (International 

Rainy Lake Board of Control, 1999). Rule curves established 

in 2000 (hereafter referred to as the 2000 Rule Curves) set 

maximum and minimum allowable water levels on an annual 

basis (Kallemeyn and others, 2003). The 2000 Rule Curves 
2 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Figure 1. Water-level streamgage locations for Rainy Lake, Namakan Reservoir, and selected rivers.

96° 93° 90°

Lake

Superior

Inset 2 Inset 1

Manitoba

Rainy River 

Basin

Base from Minnesota Department of Natural Resources 1:24,000

Universal Transverse Mercator projection, zone 15

North American Datum of 1983

Esri Data and Maps for 9.3.1. 2006.

Rapid River

Rainy River

¬«72

¬«11

94°40' 94°20' 94°

Lake of the Woods

Ontario

Minnesota

Minnesota

Ontario

Rainy River

2

1

Inset 2

0 5 10 MILES

0 5 10 KILOMETERS

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

¬«11 #

gg

g

¬«332

¬« ¬«53 71

¬«65

¬«11

¬«217

93°40' 93°20' 93° 92°40' 92°20'

48°40'

48°20'

49°

48°

51°

48°40"

Ontario

Ontario

Minnesota

Kabetogama 

Lake

Rainy

Lake

Namakan

Lake

Sand Point

Lake

Little

Vermilion

Lake

Crane

Lake

Rainy

Lake

Seine River

T

Ontario urtle River

CANADA

UNITED STATES

CANADA

CANADA

UNITED STATES

UNITED STATES

River

Vermilion

Rainy River

Little Fork 

River

Fort Frances

International Falls

Kettle Falls Dam

Squirrel Falls Dam

Koochiching Falls Dam

Bear Portage

Gold Portage

8

16

14

15

13

12

11

10

9

7

6

5

4

3

0 5 10 MILES

0 5 10 KILOMETERS

Inset 1

EXPLANATION

Active streamgage with map number (table 1)

Discontinued streamgage with map number (table 1)

1

16#

#

#

#
Introduction 3

account for natural seasonal fluctuations in water level while 

balancing the requirements for several legally recognized 

water uses within the basin (Kallemeyn and others, 2003). 

Streamgages throughout Rainy Lake and Namakan Reservoir 

(fig. 1) are used to monitor water levels for compliance with 

the 2000 Rule Curves; however, monitoring has been complicated because water-surface elevations at these streamgages 

are referenced to several different vertical datums (table 1). In 

this report, “elevation” will refer to a measurement or height 

relative to a specified datum. Without comparable elevation 

data, water-resource managers cannot develop accurate digital 

elevation models or hydraulic models that describe the movement of water through the basin (Densmore and others, 2013; 

Stevenson and Thompson, 2013); furthermore, during periods 

of high inflow, water levels in the lower Namakan Reservoir 

may differ from water levels in the upper Namakan Reservoir 

by as much as 0.3 meter (m), creating situations in which the 

lower part of the reservoir are within the rule curve band, 

whereas the upper part of the reservoir is well above the rule 

curve band. Therefore, obtaining accurate and precise elevation data referenced to a single vertical datum is critical to 

understanding and managing water levels in Rainy Lake and 

Namakan Reservoir.

In October 2014, the U.S. Geological Survey (USGS), 

Natural Resources Canada (NRCan), IJC, and National Park 

Service began a joint field study with the goal of obtaining 

precise elevations referenced to a uniform vertical datum for 

all reference marks used to set water levels at streamgages 

Table 1. Information about streamgages in Rainy Lake, Namakan Reservoir, and selected rivers in Minnesota, Unites States, and 

Ontario, Canada.

[EC, Environment Canada; LOW, Lake of the Woods Vertical Datum; USGS, U.S. Geological Survey; NGVD 1929, National Geodetic Vertical Datum of 

1929; NA, seasonal biological site—data not publicly accessible; Assumed datum, arbitrary elevation used to set water levels at streamgages; SRFN, Seine 

River First Nation; USC & GS 1912; United States Coast and Geodetic Survey Datum of 1912; NAVD 88, North American Vertical Datum of 1988; 

MSL 1912, Mean Sea Level datum of 1912;]

Map 

number 

(fig. 1)

Station number Station name Agency Vertical datum Start date End date

1 05PC021 Rainy River at Rainy River EC LOW 1–Nov–1991 Active.

2 05133500 Rainy River at Manitou Rapids, MinnesotaUSGS NGVD 1929 10–Nov–1934 Active.

3 05PC024 Rainy River at Pithers Point site no. 1 EC USC & GS 

1912

13–Oct–2011 Active.

4 05PB007 Rainy Lake near Fort Frances EC USC & GS 

1912

20–Aug–1911 Active.

5 05PB023 Rainy Lake at Northwest Bay EC Assumed datum 13–Oct–2011 Active.

6 05PB024 Rainy Lake near Bear Pass EC USC & GS 

1912

31–May–1988 Active.

7 05PB014 Turtle River near Mine Centre EC Assumed datum 1–Aug–1914 Active.

8 SRFN1 Seine River biological site SRFN NA NA NA

9 05PA013 Namakan Lake at Squirrel Island EC USC & GS 

1912

23–May–2007 Active.

10 05129290 Gold Portage outlet from Kabetogama 

Lake Near Ray, Minnesota

USGS USC & GS 

1912

14–Oct–1982 Active.

11 482611092483801 Kabetogama Lake, east end, near Old 

Dutch Bay

USGS Assumed datum 3–Nov–2010 3–Oct–2012

12 482147092291701 Sand Point Lake below Harrison Narrows 

near Crane Lake, Minnesota1

USGS NAVD 88 29–Aug–2011 22–Oct–2012

13 482042092282501 Sand Point Lake above Harrison Narrows 

Near Crane Lake, Minnesota1

USGS NAVD 88 29–Aug–2011 22–Oct–2012

14 CNLM5 Crane Lake at Crane Lake, Minnesota USACE MSL 1912 15–Jan–2000 Active.

15 481818092254201 Little Vermilion Lake above Little Vermilion Narrows1USGS NAVD 88 29–Aug–2011 22–Oct–2012

16 05129115 Vermilion River near Crane Lake, MinnesotaUSGS Assumed datum 15–Aug–1979 Active.

1

Station only operated during open-water periods.
4 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

throughout Rainy Lake and Namakan Reservoir. In this 

study, the USGS and NRCan used geodetic-quality global 

navigation satellite system (GNSS) receivers to complete 

simultaneous static surveys on 16 streamgage reference marks 

and 1 National Geodetic Survey cooperative base network 

control station in the Rainy River, Rainy Lake, Namakan 

Reservoir, and tributaries of Rainy and Crane Lakes using 

established methodologies (Canadian Geodetic Survey, 2003, 

2013; Rydlund and Densmore, 2012). 

The objective of this study was to obtain precise elevations referenced to the Canadian Geodetic Vertical Datum of 

2013 (CGVD2013) for 16 streamgage reference marks used 

to establish water levels at streamgages throughout the Rainy 

River Basin (table 1). In total, 11 of the reference marks were 

used to establish water levels for active streamgages that 

provide real-time, continuous water-level data; 5 of the reference marks surveyed were used to establish water levels for 

discontinued, temporary streamgages operated during previous studies. Discontinued streamgages used transducers that 

recorded changes in water levels by measuring changes in the 

pressure and temperature of the water surrounding the transducer. Three of the four discontinued, temporary streamgages 

only operated during open-water periods. Active streamgages 

are operated by the USGS, U.S. Army Corps of Engineers 

(USACE), and Environment Canada (EC). The final reference 

mark surveyed was National Geodetic Survey (NGS) cooperative base network control station AC4984 (map number 17), a 

reference mark of known elevation that was used as a qualitycontrol reference mark (table 2; fig. 2). 

Purpose and Scope

This report was prepared by the USGS in cooperation 

with NRCan, the IJC, and the National Park Service. The purposes of this report are to (1) describe the field surveys used to 

collect GNSS data for 17 reference marks in the Rainy River 

Basin (fig. 1), (2) describe how GNSS data were processed to 

determine water-surface elevations for all streamgages surveyed in this study, (3) present corrections to convert waterlevel data previously collected at the streamgages to watersurface elevations referenced to a uniform vertical datum, and 

(4) outline factors to consider when applying corrections to 

previously collected water-level data. The study is limited to 

the 16 streamgages in the Rainy River Basin associated with 

reference marks that were surveyed in this study; however, 

additional studies could expand the scope of this study to 

include additional tributary streamgages within the Rainy 

River Basin. In addition, a similar approach could be used in 

other basins that have streamgages referenced to a variety of 

vertical datums.

Physical Setting

The study area includes the Rainy, Turtle, Seine, and 

Vermilion Rivers; Rainy Lake; and the five lakes that compose 

Namakan Reservoir: Crane, Little Vermilion, Sand Point, 

Kabetogama, and Namakan Lakes (fig. 1). The Vermilion 

River flows into Crane Lake at the upper end of Namakan Reservoir. Crane and Little Vermilion Lakes flow into Sand Point 

Table 2. Location information for the National Geodetic Survey cooperative base network control station, 

Canadian Active Control Stations, and Continuously Operating Reference Stations used to postprocess data 

collected from global navigation satellite system receivers in this study

[Station ID, alpha-numeric descriptor assigned to each station; NGS, National Geodetic Survey cooperative base network control 

station; CACS, Canadian Active Control Station; CORS, Continuously Operating Reference Station]

Map 

number 

(fig. 2)

Station ID Station location Type of station

Latitude

(degree/minute/

second)

Longitude

(degree/minute/

second)

17 AC4984 Crane Lake, Minnesota NGS N 48 15 09.72616 W 92 29 14.96555

18 ALGO Algonquin Park, Ontario CACS N 45 57 20.84731 W 78 04 16.90648

19 DUBO Lac Du Bonnet, Manitoba CACS N 50 15 31.68253 W 95 51 58.20777

20 FLIN Flin Flon, Manitoba CACS N 54 43 32.07415 W 101 58 40.86832

21 PICL Pickle Lake, Ontario CACS N 51 28 47.27895 W 90 09 43.06934

22 GDMA Grand Marais, Minnesota CORS N 47 44 54.75711 W 90 20 28.47144

23 MNAS Ash Lake, Minnesota CORS N 48 17 38.54626 W 92 58 13.42650

24 MNBD Birchdale, Minnesota CORS N 48 37 39.67691 W 94 04 02.15729

25 MNMG Margie, Minnesota CORS N 48 08 04.54490 W 93 52 42.50778

26 MNRV Roosevelt, Minnesota CORS N 48 47 21.79724 W 95 03 04.45950

27 MNSQ Squaw Lake, Minnesota CORS N 47 36 13.44132 W 94 07 36.20907

28 MNVI Virginia, Minnesota CORS N 47 31 23.77164 W 92 33 41.43356

29 MNWH Waskish, Minnesota CORS N 48 09 00.63600 W 94 30 42.99689

30 ROSS Rossport, Ontario CORS N 48 50 01.39381 W 87 31 10.52238

31 YWG1 Winnipeg, Manitoba CORS N 49 54 02.06942 W 97 15 33.82364
Introduction 5

Lake; Sand Point Lake flows into Namakan Lake; and water 

moves bidirectionally between Namakan and Kabetogama 

Lakes depending on lake levels, wind direction, inflows from 

tributaries, and dam regulation (Christensen and others, 2013). 

Water flows from Namakan and Kabetogama Lakes into 

Rainy Lake from outflows at Kettle and Squirrel Falls Dams 

and at Gold Portage outlet, respectively. Rainy Lake is fed by 

Namakan Reservoir and several tributary rivers. The Seine and 

Turtle Rivers are the two largest tributaries that enter Rainy 

Lake downstream from the outflows from Namakan Reservoir 

into Rainy Lake (Kallemeyn and others, 2003). Rainy Lake 

drains into Rainy River at the southwestern corner of Rainy 

Lake, and the Rainy River flows northwest into Lake of the 

Woods. Rainy River, the southern basin of Rainy Lake, and 

Namakan Reservoir form the international border between the 

United States and Canada. 

Water levels in Rainy River, Rainy Lake, and Namakan 

Reservoir are controlled by three dams. The Koochiching 

Falls Dam controlling Rainy River flow out of Rainy Lake is 

located between Fort Frances, Ontario, and International Falls, 

Minnesota. This dam is the source of hydroelectric power for 

the Boise Cascade Corporation’s paper pulp industrial facilities. Two dams control the flow of water from Namakan Lake 

into Rainy Lake: Kettle Falls and Squirrel Falls Dams (International Rainy Lake Board of Control, 1999). The parts of 

Kettle Falls and Koochiching Falls Dams located in the United 

States are owned by the Boise Cascade Corporation, and the 

Canadian part is owned by Abitibi Consolidated Incorporated. 

!(

!(

!(

!(

!(

!(

!(

!(

!(

!(

!( !(

!(

!(

!(

Saskatchewan

Pennsylvania

31

30

29

28 27

26

25

24

23 22

21

20

19

18

17

Iowa

South Dakota

Wisconsin

North Dakota

Michigan New York

Michigan

Ontario

Manitoba

105° 100° 95° 90°0 85° 80° 75°

55°

50°

45°

!(

Minnesota

Lake of the Woods

Rainy River Basin

Quebec

Hudson Bay

Lake Superior

Lake 

Michigan

Lake Huron

Lake Erie

Lake Ontario

Georgian

Bay

17

31

0 125 250 MILES

0 150 300 KILOMETERS

 EXPLANATION

Continuously-operating reference station with 

 map number (table 2)

Canadian active control system station with 

 map number (table 2) 

Cooperative base network control station with 

 map number (table 2) 

21(!

(!

(!

Base from Minnesota Department of Natural Resources 1:24,000

Universal Transverse Mercator projection, zone 15

North American Datum of 1983

Esri Data and Maps for 9.3.1. 2006.

CANADA

UNITED STATES

fig02.ai Figure 2. Locations of the National Geodetic Survey cooperative base network control station, Canadian Active Control Stations, and 

Continuously Operating Reference Stations used to postprocess data collected from global navigation satellite system receivers in 

this study.
6 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

In addition to the regulated outflows at Kettle and Squirrel 

Falls, overflows from Namakan Lake into Rainy Lake happen 

at Bear and Gold Portages.

Methods

Methods are described in the following four sections 

of this report. The first section details how GNSS receivers 

were deployed and how field data were collected. The second 

section details the processing methods used by NRCan and 

USGS to obtain elevations for the surveyed reference marks. 

All elevations reported in the second section were measured to 

the nearest 0.001 m. The third section describes how elevations of reference marks were used to develop offsets, which 

are values added to or subtracted from published water levels 

in order to convert water-level data to elevations referenced 

to CGVD2013. The fourth section details how offsets were 

applied to published water levels and how corrected elevations 

were used to compare and evaluate collected water-level data 

from streamgages throughout the study area.

Field Data Collection

Three field crews deployed 17 geodetic-quality global 

positioning system GNSS receivers paired with choke ring 

antennas statically for satellite data collection. The GNSS 

units for data collection were deployed from October 5, 2014 

(day of year 278), through October 9, 2014 (day of year 282), 

at 16 specified streamgage locations (fig. 1) and 1 NGS cooperative base network control station (map number 17; fig. 2) 

for additional quality assurance. The exact start and end dates 

and times for each GNSS unit are available electronically in 

table 1–1 of appendix 1; GNSS units were deployed to provide 

as much simultaneous data collection time as possible among 

all surveyed sites and minimize variability related to weather 

conditions and satellite positions. The log files from the GNSS 

surveys are available electronically in appendix 1.

Field data-collection procedures used during the survey 

followed guidelines established for static network surveys 

as described by compatible methods from NRCan (Canadian 

Geodetic Survey, 2003, 2013) and the USGS (Rydlund and 

Densmore, 2012). When a clear view of surrounding satellites was possible, GNSS units were deployed directly above 

existing reference marks used to establish water levels at 

streamgages; however, at locations where a clear view of surrounding satellites was obstructed by tree cover or topographical relief, GNSS units were deployed nearby to improve the 

quality of satellite signal reception and reduce satellite signal 

multipath. Multipath is a condition in which the accuracy of 

collected satellite data diminishes because the satellite signal 

arrives at the receiver antenna by way of several different 

paths (Georgiadou and Kleusberg, 1988). Bodies of water 

can create reflective surfaces that cause multipath issues. For 

view-obstructed locations where reference marks could not 

be surveyed directly, surveyor level loops (also referred to as 

spirit level circuits) were used to accurately measure elevation differences between points surveyed with GNSS and 

streamgage reference marks (Kenney, 2010; Canadian Geodetic Survey, 2013). Instantaneous water levels were obtained 

at each site using either readings from operating streamgages 

(Environment Canada, 2015; U.S. Army Corps of Engineers, 

2015; U.S. Geological Survey, 2015) or direct measurement 

from an established reference mark using surveyor level loops.

Data Processing

Elevations as defined by ellipsoid, geoid, and orthometric 

heights are all attempts to model the shape of the Earth using 

real world coordinates. An ellipsoid is a spherical shape with a 

polar radius that is shorter in length than the equatorial radius, 

and the overall shape of the Earth is best predicted using an 

ellipsoid (Li and Götze, 2001). Ellipsoid heights are offsets 

above or below a reference ellipsoid. A geoid is a model that 

represents the Earth’s mean global sea level under the influence of gravitation and rotation alone (Milbert and Smith, 

1996), and each vertical datum is associated with a particular 

geoid. Geoid heights are applied to ellipsoid heights to obtain 

orthometric heights, which refer to elevations above sea level 

referenced to the vertical datum associated with the geoid 

model. 

The GNSS data collected at control and reference stations 

(fig. 2; table 2) were used to determine three-dimensional 

coordinates (latitude, longitude, and ellipsoid heights). Both 

NRCan and USGS postprocessed GNSS data were collected 

in receiver independent exchange (also known as RINEX) 

format independently using different methods in order to 

provide a quality comparison. The horizontal reference frames 

used by Canada (North American Datum of 1983 [NAD 83]; 

Canadian Spatial Reference System [CSRS]) and the United 

States (NAD 83 [2011] reference frame in epoch 2010.00) are 

compatible and equivalent for the purposes of this study. 

Satellite data were processed by NRCan staff using 

Bernese GNSS Software v5.2 (BSW; Dach and others, 

2007; Dach and Walser, 2015), a relative positioning method 

whereby coordinated differences between pairs of points 

(baselines) are computed. Although BSW is capable of 

processing data from the Russian Global Orbiting Navigation Satellite System (GLONASS), the GLONASS data were 

not processed in this study. Using BSW, three-dimensional 

coordinates (latitude, longitude, and ellipsoid heights) were 

determined for the 16 streamgage reference marks and NGS 

cooperative base network control station AC4984 in the geometric reference frame of NAD 83 (CSRS) Velocity Grid v6 

for epoch 2010.0. 

Data from four Canadian Active Control System (CACS; 

Natural Resources Canada, 2016) stations were included to 

provide a connection to the NAD 83 reference frame and the 

international terrestrial reference frame (also known as ITRF) 

in order to obtain specific coordinates (table 2); the CACS 
Methods 7

stations included ALGO (Algonquin Park, Ontario), DUBO 

(Lac Du Bonnet, Manitoba), FLIN (Flin Flon, Manitoba), and 

PICL (Pickle Lake, Ontario). Seven other CACS stations and 

NGS Continuously Operating Reference Stations (CORS; 

National Geodetic Survey, 2014a) were included as local 

quality-control points; however, a substantial part of available data from these stations could not be used because signal 

obstructions prohibited common satellites from being in view 

at both ends of the baseline, and these seven stations were not 

used in the study. 

Session baselines from BSW were corrected for relative 

crustal motion between the observation epoch and the 2010.0 

reference epoch using the adopted NAD 83 (CSRS) Velocity Grid v6 (Craymer and others, 2011). Such crustal motions 

between local stations and CACS stations that are much farther away can substantially affect reference frame realization. 

Estimated session baselines were combined into a network 

adjustment using NRCan GHOST software (Beattie, 1987), 

and CACS stations were weighted to known NAD 83 (CSRS) 

Velocity Grid v6 coordinates at epoch 2010.0 using known 

accuracies. The Canadian Gravimetric Geoid model of 2013 

(CGG2013) was applied to postprocessed ellipsoid heights 

to obtain orthometric heights referenced to CGVD2013 for 

all streamgage reference marks and NGS cooperative base 

network control station AC4984 (Huang and Véronneau, 2013; 

Véronneau and others, 2014a, 2014b). 

The USGS postprocessed the GNSS data through the 

NGS Online Positioning Users Service (OPUS; National 

Geodetic Survey, 2014b), a service that uses the NGS PAGES 

processing software (National Geodetic Survey, 2015a), with 

baseline processing methodology similar to BSW. Using 

OPUS-Projects (National Geodetic Survey, 2014c), a network adjustment was applied to the 16 streamgage reference 

marks and NGS cooperative base network control station 

AC4984 using 10 CORS to define the NAD 83 (2011) reference frame in epoch 2010.0 (table 2); the CORS used in the 

network adjustment included GDMA (Grand Marais, Minnesota), MNAS (Ash Lake, Minn.), MNBD (Birchdale, Minn.), 

MNMG (Margie, Minn.), MNRV (Roosevelt, Minn.), MNSQ 

(Squaw Lake, Minn.), MNVI (Virginia, Minn.), MNWH 

(Waskish, Minn.), ROSS (Rossport, Ontario), and YWG1 

(Winnipeg, Manitoba; National Geodetic Survey, 2014a). 

Using OPUS, the USGS established known geodeticquality coordinates for each reference mark (Rydlund and 

Densmore, 2012); coordinate information for each reference 

mark includes NAD 83 (2011 epoch 2010.00), latitude, longitude, and ellipsoid heights (National Geodetic Survey, 2012). 

Geoid model 12A (National Geodetic Survey, 2015b) was 

applied to postprocessed ellipsoid heights to obtain orthometric heights referenced to the North American Vertical Datum 

of 1988 (NAVD 88; Zilkoski and others, 1992); however, 

after processing session baselines, more than one-half of the 

available data were omitted by OPUS based on automated data 

quality criteria established by the NGS. As a result, as little 

as 13 hours of data were used to process session baselines 

for some reference marks. In addition, the CORS of MNAS, 

MNBD, MNMG, MNRV, MNSQ, and MNWH have modeled 

velocities that do not include vertical velocities; therefore, 

corrections for vertical crustal motion cannot be applied uniformly across the area covered by the CORS for data processed in OPUS-Projects by the USGS. In contrast, processing 

completed by NRCan using BSW included corrections for 

vertical crustal motion applied to all processed baselines and 

estimated coordinates.

Development of Streamgage Datum Offsets

Orthometric heights obtained from processing collected 

GNSS data were used to develop offsets that convert published water levels to elevations referenced to CGVD2013, 

either through direct streamgage reference mark surveys or 

surveyor level loops between surveyed points and streamgage 

reference marks. Offsets are based on published water levels, 

so the magnitude of each offset depends on whether water 

levels are published as actual elevations or as local datums 

that allow smaller numbers to be used for publication. For 

example, USGS station 05129290 (Gold Portage outlet from 

Kabetogama Lake near Ray, Minnesota; map number 10) (fig. 

1) was established using the U.S. Coast and Geodetic Survey 

Datum of 1912; however, water levels are published as elevations minus 1,100 feet (U.S. Geological Survey, 2015). The 

offset for USGS station 05129290, therefore, will be much 

larger compared to the offset for USACE station CNLM5 

(Crane Lake at Crane Lake, Minnesota; map number 14) 

(fig. 1), which are published as elevations in 1912 Mean Sea 

Level datum (U.S. Army Corps of Engineers, 2015). Offset data are presented in metric (International System) and 

English (U.S. customary) units. The vertical datums used to 

establish water levels for streamgages examined in this study 

are presented in table 1.

Application of Streamgage Datum Offsets

Streamgage datum offsets were applied to surveyed 

streamgages, and water-surface elevations referenced to 

CGVD2013 were compared among active streamgages in 

Namakan Reservoir; Rainy Lake; and the Vermilion, Turtle, 

and Rainy Rivers (fig. 1). In addition, because three of the four 

temporary streamgages in the Namakan Reservoir were only 

operated during open water periods between the start and end 

dates shown in table 1, the period from May 1, 2012, through 

September 30, 2012, was used to compare water-surface 

elevations among all active and discontinued streamgages in 

Namakan Reservoir. This period represents the most recent 

period when all active and discontinued streamgages in 

Namakan Reservoir operated simultaneously. Monthly mean 

water-surface elevations (referenced to CGVD2013) were 

compared among all streamgages in Namakan Reservoir in 

order to average variability in the data associated with the temporary streamgage installations.
8 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Global Navigation Satellite System 

Surveys

Deployment times for GNSS units ranged from 29 to 

68 hours, with a mean deployment time of 46 hours. Satellite 

data quality was generally good during the GNSS surveys. 

Despite the best efforts of the field crews to find locations with 

a clear view of surrounding satellites, steep terrain and dense 

tree cover surrounding some of the streamgage locations interfered with satellite coverage during certain times of the day. 

In addition, proximity of the GNSS units to the water surface 

created multipath issues that had to be accounted for during 

data processing. Surveyor level loops between GNSS survey 

points and reference marks of known elevation referenced to 

a specified vertical datum likely introduced a small amount of 

error (less than or equal to 0.005 m) into the elevation data. 

Comparisons of water-surface elevations at surveyed 

streamgages only will be presented in metric units (meters). 

Data processing files are included in appendix 2. The measured ellipsoid and orthometric heights of 17 survey locations 

processed using NRCan and USGS methods are presented 

in table 3. Surveyor level loop information between GNSSsurveyed points and streamgage reference marks are in appendix 3.

The NAD 83 ellipsoid heights obtained using NRCan and 

USGS processing methods closely approximated each other 

(table 3) even though the USGS did not apply corrections for 

Table 3. Global Navigation Satellite System survey results for 16 streamgage reference marks and National Geodetic Survey 

cooperative base network control station AC4984, processed using Natural Resources Canada and U.S. Geological Survey methods.

[NRCan, Natural Resources Canada; USGS, U.S. Geological Survey; Ellipsoid height, offsets above or below a reference ellipsoid that represents the shape 

of the Earth; m, meter; CGG2013, correction for the Canadian Gravimetric Geoid of 2013 applied to ellipsoid heights to obtain elevations referenced to the 

Canadian Geodetic Vertical Datum of 2013 (CGVD2013); Orthometric height, elevation above sea level referenced to the vertical datum corresponding to the 

applied geoid; 12A, elevation correction for Geoid 12A applied to ellipsoid heights to obtain elevations referenced to the North American Vertical Datum of 

1988 (NAVD 88); no., number]

Map 

number 

(figs. 1 

and 2)

Station number Station name

NRCan USGS

Ellipsoid 

height 

(m)

CGG2013 

(m)

Orthometric 

height1

(m)

Ellipsoid 

height 

(m)

12A 

(m)

Orthometric 

height2

(m)

1 05PC021 Rainy River at Rainy River 296.952 28.295 325.247 296.959 29.077 326.036

2 05133500 Rainy River at Manitou Rapids, 

Minnesota

311.001 29.028 340.029 310.998 29.792 340.790

3 05PC024 Rainy River at Pithers Point site no. 1 307.964 30.013 337.977 307.972 30.817 338.789

4 05PB007 Rainy Lake near Fort Frances 309.039 30.130 339.169 309.041 30.920 339.961

5 05PB023 Rainy Lake at Northwest Bay 307.412 29.962 337.374 307.424 30.743 338.167

6 05PB024 Rainy Lake near Bear Pass 306.839 30.796 337.635 306.848 31.561 338.409

7 05PB014 Turtle River near Mine Centre 315.727 31.302 347.029 315.714 32.062 347.776

8 SRFN1 Seine River biological site 307.101 31.636 338.737 307.110 32.374 339.484

9 05PA013 Namakan Lake at Squirrel Island 319.136 30.915 350.051 319.163 31.684 350.847

10 05129290 Gold Portage outlet from Kabetogama 

Lake Near Ray, Minnesota

309.624 30.361 339.985 309.646 31.151 340.797

11 482611092483801 Kabetogama Lake, east end, near Old 

Dutch Bay

311.975 30.584 342.559 311.989 31.366 343.355

12 482147092291701 Sand Point Lake below Harrison 

Narrows near Crane Lake, Minnesota

309.554 30.855 340.409 309.599 31.634 341.233

13 482042092282501 Sand Point Lake above Harrison 

Narrows Near Crane Lake, 

Minnesota

315.242 30.837 346.079 315.259 31.617 346.876

14 CNLM5 Crane Lake at Crane Lake, Minnesota 311.226 30.705 341.931 311.234 31.482 342.716

15 481818092254201 Little Vermilion Lake above Little 

Vermilion Narrows

309.788 30.811 340.599 309.785 31.589 341.374

16 05129115 Vermilion River near Crane Lake, 

Minnesota

326.747 30.585 357.332 326.773 31.371 358.144

17 AC4984 Cooperative Base Network Control 

Station

344.628 30.657 375.285 344.632 31.434 376.066

1

Elevation referenced to CGVD2013.

2

Elevation referenced to NAVD 88.
Global Navigation Satellite System Surveys 9

vertical crustal motion to processed baselines or estimated 

coordinates; corrections for vertical crustal motion may be 

plus or minus (±) 0.003 meter per year depending on the location within the study area (Henton and others, 2006; Craymer, 

2006; Snay and Pearson, 2010). Ellipsoid heights obtained 

using USGS methods generally were higher than ellipsoid 

heights obtained using NRCan methods. Differences between 

methods ranged from -0.003 to +0.045 m, with a mean difference of 0.011 m; furthermore, determined ellipsoid heights for 

NGS cooperative base network control station AC4984 (map 

number 17) closely approximate published values (National 

Geodetic Survey, 2015c). An ellipsoid height of 344.633 

m was determined for station AC4984 during the last static 

GNSS survey done by the NGS in 1996 (National Geodetic 

Survey, 2015c). Ellipsoid heights of AC4984 determined using 

NRCan and USGS processing methods were 344.628 m and 

344.632 m, respectively. Offsets were developed using GNSS 

survey point elevations and surveyor leveling information 

(appendix 3).

A summary of streamgage offset values is presented in 

table 4. Site 8 is not included in table 4 because information 

available about the streamgage was not sufficient to develop 

an offset. Offsets presented in this report can be used in the 

evaluation of rule curves and in flood damage curves that fully 

assess the benefits of one regulation approach over another. 

In addition, offsets may be used to calibrate hydraulic models 

developed for four narrows that connect lakes of Namakan 

Reservoir, refine digital elevation models, and support 

modeling studies designed to assess the effects of rule curves 

on aquatic vegetation, benthic invertebrates, northern pike 

(Esox Lucius), and walleye (Sander vitreus). Because Canada 

recently adopted a national reference standard for elevations 

(Véronneau and others, 2014a, 2014b) that is based on a geoid 

model and compatible with GNSS positioning, the NRCan 

method was selected over the USGS method for developing offsets between published streamgage water levels and 

CGVD2013 elevations; furthermore, elevations referenced to 

CGVD2013 will be useful to other ongoing studies being completed by NRCan. Instantaneous water-level measurements 

in published streamgage format and instantaneous watersurface elevations in CGVD2013 are available in appendix 3. 

Subsequent comparisons of water-surface elevations among 

streamgages will be referenced to CGVD2013 and presented 

in metric units (meters).

Table 4. Offsets to convert published water levels to water-surface elevations referenced to the Canadian Geodetic Vertical Datum 

of 2013 for streamgages in Rainy Lake, Namakan Reservoir, and selected rivers.

[Published data type, descriptor of type of water-level data published at a streamgage; Offset, the value to be added or subtracted to water-level data to convert 

published streamgage data to elevations in Canadian Geodetic Vertical Datum of 2013; EC, Environment Canada; Elevation, water levels are published as 

elevations referenced to a previously specified vertical datum; USGS, U.S. Geological Survey; Local datum, an arbitrary datum used to simplify data display 

when publishing water-level data for streamgages; no., number; USACE, U.S. Army Corps of Engineers]

Map 

number 

(fig. 1)

Station number Station name Agency Published 

data type

Published 

units

Offset

Meter Foot

1 05PC021 Rainy River at Rainy River EC Elevation Meter -0.361 -1.18

2 05133500 Rainy River at Manitou Rapids, Minnesota USGS Local datum Foot +323.475 +1,061.27

3 05PC024 Rainy River at Pithers Point site no. 1 EC Elevation Meter -0.637 -2.09

4 05PB007 Rainy Lake near Fort Frances EC Elevation Meter -0.608 -1.99

5 05PB023 Rainy Lake at Northwest Bay EC Local datum Meter +328.315 +1,077.15

6 05PB024 Rainy Lake near Bear Pass EC Elevation Meter -0.599 -1.97

7 05PB014 Turtle River near Mine Centre EC Local datum Meter +344.176 +1,129.19

9 05PA013 Namakan Lake at Squirrel Island EC Elevation Meter -0.613 -2.01

10 05129290 Gold Portage outlet from Kabetogama 

Lake Near Ray, Minnesota

USGS Local datum Foot +334.701 +1,098.10

11 482611092483801 Kabetogama Lake, east end, near Old 

Dutch Bay

USGS Local datum Foot +334.384 +1,097.06

12 482147092291701 Sand Point Lake below Harrison Narrows 

near Crane Lake, Minnesota

USGS Elevation Foot -0.820 -2.69

13 482042092282501 Sand Point Lake above Harrison Narrows 

Near Crane Lake, Minnesota

USGS Elevation Foot -0.802 -2.63

14 CNLM5 Crane Lake at Crane Lake, Minnesota USACE Elevation Foot -0.597 -1.96

15 481818092254201 Little Vermilion Lake above Little Vermilion NarrowsUSGS Elevation Foot -0.808 -2.65

16 05129115 Vermilion River near Crane Lake, 

Minnesota

USGS Local datum Foot +352.769 +1,157.38
10 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Survey Comparisons

Offsets developed to correct measured water-level data 

to elevations above sea level referenced to CGVD2013 were 

applied to collected water-level data from active and discontinued streamgages in the study area. Daily mean water 

levels during the survey period were compared among active 

streamgages on Namakan Reservoir, Rainy Lake, and surveyed rivers (fig. 1). In addition, monthly mean water levels 

from 2012 were compared for all active and discontinued 

streamgages in Namakan Reservoir. Monthly mean water 

levels were used to reduce variability associated with temporary installations, and data from 2012 were used because 2012 

represents the most recent period when all active and discontinued streamgages ran simultaneously. 

Namakan Reservoir

Active, continuous streamgages for Namakan Reservoir operate at Crane Lake (map number 14; USACE station CNLM5), the Gold Portage outlet of Kabetogama Lake 

(map number 10; USGS station 05129290), and Squirrel 

Island near the outlet of Namakan Lake (map number 9; EC 

station 05PA013) (fig. 1). Boxplots of water-surface elevations (referenced to CGVD2013) during the data collection 

period (October 5–9, 2014) at active streamgages in Namakan 

Reservoir are presented in figure 3. Mean water-surface elevations decreased from upstream to downstream among all three 

stations.

Rainy Lake

Active streamgages in Rainy Lake operate near Bear Pass 

(map number 6; EC station 05PB024), at Northwest Bay (map 

number 5; EC station 05PB023), and near Fort Frances (map 

number 4; EC station 05PB007) (fig. 1). Water-surface elevation data (referenced to CGVD2013) for the data collection 

period (October 5–9, 2014) at active streamgages in Rainy 

Lake are presented in figure 4. Mean water-surface elevations 

during the data collection period were similar among all three 

stations.

Rivers

Rivers with active streamgages surveyed in this study 

include the Vermilion, Turtle, and Rainy Rivers (fig. 1). A 

bar chart of mean water-surface elevations (referenced to 

CGVD2013) for active river streamgages surveyed in this 

study are presented in figure 5; mean water-surface elevations 

were determined by taking the mean of continuous water level 

data collected October 5–9, 2014, at each streamgage and 

applying the appropriate offsets. Vermilion River near Crane 

Lake, Minnesota (map number 16; USGS station 05129115) 

and the Turtle River near Mine Centre (map number 7; EC 

station 05PB014) represent inflow streamgages to Namakan 

Reservoir and Rainy Lake, respectively. Water-surface elevations at the inflow streamgages are substantially higher than 

the water-surface elevations of Namakan Reservoir (fig. 3) and 

Rainy Lake (fig. 4). Starting at the outlet of Rainy Lake and 

moving downstream towards Lake of the Woods, Rainy River 

streamgages were surveyed at Pithers Point (map number 3; 

EC station 05PC024), Manitou Rapids (map number 2; USGS 

station 05133500), and the town of Rainy River, Ontario (map 

number 1; EC station 05PC021) (fig. 1). Water-surface elevations at the outlet of Rainy Lake (map number 3; EC station 

05PC024) were slightly lower in elevation than Rainy Lake 

(fig. 4), and a substantial drop in elevation (more than 10 m) 

was observed between Pithers Point (map number 3; EC station 05PC024) and Manitou Rapids (map number 2; USGS 

station 05133500). A smaller drop in elevation (about 2 m) 

was observed between Manitou Rapids (map number 2; USGS 

station 05133500) and the town of Rainy River, Ontario (map 

number 1; EC station 05PC021).

2012 Namakan Reservoir Data

Because surveyed temporary streamgages were discontinued, boxplots of monthly water-level data collected in 2012 

were compared for all active and discontinued streamgages 

in the Namakan Reservoir (fig. 1). Boxplots of monthly 

water-surface elevations referenced to CGVD2013 for May 

through September of 2012 are presented in figure 6. Elevations generally decrease from upstream to downstream, 

with the most notable exception being the temporary indexvelocity streamgage used to measure flow between Namakan 

and Kabetogama Lakes (map number 11; USGS station 

482611092483801). In addition, water-surface elevations for 

the temporary streamgage at Sand Point Lake below Harrison 

Narrows (map number 12; USGS station 482147092291701) 

seem to be lower than elevations at the outlet sites at Squirrel 

Island (map number 9; EC station 05PA013) and Gold Portage 

(map number 10; USGS station 05129290).

The observed water levels at discontinued streamgages 

482611092483801 (map number 11) and 482147092291701 

(map number 12) do not make sense hydrologically given the 

direction of flowing water, which indicates that the transducers may have shifted on the lake bottoms or that initial water 

levels may have been established incorrectly. A time mismatch 

could have happened when programming the water levels 

into the transducers based on a measurement from a reference 

point of known elevation. During windy and wavy conditions, water levels can vary by as much as ±0.060 m (U.S. 

Geological Survey, 2015), and there is a delay associated with 

programming water levels into the transducers. If a reference point is measured during the trough of the waves and is 

applied to the transducer during the peak of the waves, then 

the transducer readings will read consistently low. Similarly, if 
Survey Comparisons 11

a reference point is measured during the peak of the waves and 

is applied to the transducer during the trough of the waves, 

then the transducer will read consistently high. 

Published daily mean water-surface elevations (referenced to NAVD 88) from 2012 were compared for the 

two discontinued streamgages on Sand Point Lake (map 

numbers 12 and 13; USGS stations 482147092291701 and 

482042092282501, respectively) to further address the hydrologic discrepancy observed at USGS station 482147092291701 

(map number 12; fig. 7). Changes in water levels associated 

with precipitation and changes in dam regulation track perfectly between the two streamgages (fig. 7), and water-surface 

elevations measured manually during site visits that happened 

on the same day were identical or demonstrated substantial 

14−CNLM5

9−05PA013

10−05129290

339.75

339.80

339.85

339.90

339.95

Elevation referenced to Canadian Geodetic 

Vertical Datum of 2013, in meters

24 54 96

October 5 October 6 October 7 October 8 October 9 14−CNLM5 9−05PA013 10−05129290

24 58 96

14−CNLM59−05PA013

10−05129290

24 68 96

Map number and station number (table 1)14−CNLM5

9−05PA013

10−05129290

24 61 96

14−CNLM5

9−05PA013

10−05129290

25 58 96

fig03.ai

32 Number of values

EXPLANATION

Maximum value

75th percentile

50th percentile

 (median)

25th percentile

Minimum value

Figure 3. Water-surface elevation data referenced to the Canadian Geodetic Vertical Datum of 2013 for the data collection 

period (October 5–9, 2014) at active streamgages in Namakan Reservoir, which are identified using map and station numbers 

associated with data in table 1.
12 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Figure 4. Water-surface elevation data referenced to the Canadian Geodetic Vertical Datum of 2013 for the data collection 

period (October 5–9, 2014) at active streamgages in Rainy Lake, which are identified using map and station numbers 

associated with data in table 1. 6−05PB024 5−05PB023 4−05PB007

336.85

336.90

336.95

337.00

337.05

67 288 288

6−05PB0245−05PB0234−05PB007

60 288 276

6−05PB0245−05PB0234−05PB007

63 288 288

6−05PB0245−05PB0234−05PB007

62 276 288

6−05PB0245−05PB0234−05PB007

66 288 288

Elevation referenced to Canadian Geodetic 

Vertical Datum of 2013, in meters

Map number and station number (table 1)

October 5 October 6 October 7 October 8 October 9

fig04.ai

63 Number of values

EXPLANATION

Maximum value

75th percentile

50th percentile

 (median)

25th percentile

Minimum value
Limitations of the Study 13

overlap in observed ranges (U.S. Geological Survey, 2015). 

These data indicate that a time mismatch did not cause 

the water-surface elevation differences between the two 

streamgages observed in figure 6. The observed differences 

likely are attributable to variability associated with collected 

satellite data or variability in the instantaneous water level 

measured during the GNSS survey, which was used to develop 

the offset that corrects collected water-level data to elevations 

referenced to CGVD2013. 

Data are insufficient to similarly address if a time mismatch happened at USGS station 482611092483801 (map 

number 11). Possible causes for the observed hydrologic 

discrepancy could include a time mismatch, variability in the 

collected satellite data, and variability in the instantaneous 

water level measured during the GNSS survey, which was 

used to develop the offset that corrects collected water-level 

data to elevations referenced to CGVD2013. For active 

streamgages in the Namakan Reservoir, data collected in 

2012 (fig. 6) showed a similar pattern to data collected during 

2014 surveys when both datasets were corrected to reference 

CGVD2013 (fig. 3), indicating that active streamgages have 

remained stable with time. Finally, five of the seven surveyed 

streamgages (active and discontinued) in Namakan Reservoir demonstrated water-surface elevations that consistently 

decreased from upstream to downstream when offsets were 

applied to water-level data collected in 2012.

Limitations of the Study

Several limitations should be considered when applying 

results obtained from analyses presented in this report. Collected satellite data were compared among all sites simultaneously in order to minimize the overall error in the survey. In 

addition, elevations obtained for reference marks in this study 

are referenced to specified ellipsoid and geoid models, so 

the elevations presented in this report should not be considered absolute elevations. Geoid models CGG2013 and 12A 

were applied to ellipsoid heights presented in table 3 in order 

to obtain elevations referenced to CGVD2013 and NAVD 

88, respectively; however, only elevations referenced to 

CGVD2013 were used to develop offsets presented in table 4.

Streamgage datum offsets were developed using instantaneous water-level measurements; therefore, presented 

offsets do not account for variability associated with wind, 

wave action, dam regulation, and other factors. At active 

streamgages, continuous water-level data can be used to 

examine the relations among water-surface elevations at 

streamgages and to evaluate the accuracy of presented offsets; 

however, similar comparisons could not be made to examine 

variability with time at discontinued streamgage locations 

without going back to data collected in 2012. Comparing 

2012 water-level data corrected to elevations referenced to 

CGVD2013, elevations for two streamgages (USGS stations 482147092291701 and 482611092483801) that were 

discontinued in October 2012 did not make hydrologic sense 

compared to other streamgages (fig. 6); therefore, caution 

should be used when applying presented streamgage offsets 

to discontinued, temporary streamgages. If discrepancies 

between water-surface elevations at discontinued streamgages 

and nearby active streamgages demonstrate consistency during 

the entire period of overlapping measured record, then data 

corrections could be applied to water-level data collected at 

discontinued streamgages in order to incorporate the data into 

modeling applications and rule curve evaluations; however, 

the described analyses are beyond the scope of this report.

Figure 5. Mean water-surface elevations referenced to the 

Canadian Geodetic Vertical Datum of 2013 for the data collection 

period (October 5–9, 2014) at active streamgages on the Vermilion 

(map number 16; station 05129115), Turtle (map number 7; 05PB014), 

and Rainy (map numbers 1, 2, and 3; stations 05PC021, 05133500 

and 05PC024, respectively) Rivers; streamgages are identified 

using map and station numbers associated with data in table 1.

320

325

330

335

340

345

350

355

360

Elevation referenced to Canadian Geodetic Vertical Datum of 2013, in meters

16−05129115

7−05PB014

3−05PC024

2−05133500

1−05PC021

Map number and station number (table 1)

354.196

345.356

336.876

324.704

322.661

fig05.ai
14 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data 15−D 14−A 13−D 12−D 11−D 10−A 9−A 15−D 14−A 13−D 12−D 11−D 10−A 9−A 15−D 14−A 13−D 12−D 11−D 10−A 9−A 15−D 14−A 13−D 12−D 11−D 10−A 9−A 15−D

14−A

13−D12−D11−D

10−A

9−A

339.5

340.0

340.5

Elevation referenced to Canadian Geodetic Vertical Datum of 2013, in meters

31 30 31 31 31 31 31

May

30 29 30 30 30 30 30

June

Map number (table 1) and site status (A, active; D, discontinued)

31 31 31 31 31 31 31

July

31 31 31 31 31 31 31

August

30 30 30 30 30 30 30

September

31 Number of values

EXPLANATION

Maximum value

75th percentile

50th percentile

 (median)

25th percentile

Minimum value

Figure 6. Monthly water-surface elevation data for all active and discontinued streamgages in Namakan Reservoir during 

the open water period of 2012, converted from streamgage datums to the Canadian Geodetic Vertical Datum of 2013 using 

offsets presented in table 4; streamgages are identified using map numbers associated with data in table 1.
Limitations of the Study 15

Figure 7. Published mean daily water-surface elevations (referenced to the North American Vertical Datum of 

1988) for discontinued U.S. Geological Survey water-level streamgages on Sand Point Lake above (map number 

13; station 482042092282501) and below (map number 12; station 482147092291701) Harrison Narrows in 2012 

(data from U.S. Geological Survey, 2015).

1,116.5

1,117.0

1,117.5

1,118.0

1,118.5

1,119.0

1,119.5

Elevation referenced to North American 

Vertical Datum of 1988, in feet

May

fig07.ai

June July August September

2012

Sand Point above Harrison 

Narrows (map number 13)

Sand Point below Harrison 

Narrows (map number 12)
16 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Summary

Continuously recording water-level streamgages in Rainy 

Lake and Namakan Reservoir are used to regulate water levels 

according to rule curves established in 2000 by the International Joint Commission; however, streamgage water levels 

were referenced to a variety of vertical datums, confounding 

efforts to model the flow of water through the system, regulate 

water levels during periods of high inflow, and evaluate the 

effectiveness of the rule curves. In October 2014, the U.S. 

Geological Survey, Natural Resources Canada, International 

Joint Commission, and National Park Service began a joint 

field study with the goal of obtaining precise elevations referenced to a uniform vertical datum for all reference marks used 

to establish water-level streamgages throughout Rainy Lake 

and Namakan Reservoir.

This report was prepared by the U.S. Geological Survey 

in cooperation with Natural Resources Canada, the International Joint Commission, and the National Park Service. The 

purposes of this report are to (1) describe the field surveys 

used to collect Global Navigation Satellite System (GNSS) 

data for 16 streamgage reference marks in the Rainy River 

Basin, (2) describe how collected GNSS data were processed 

to determine water-surface elevations for all streamgages surveyed in this study, (3) present corrections to convert waterlevel data previously collected at the streamgages to watersurface elevations referenced to a uniform vertical datum, and 

(4) outline factors to consider when applying corrections to 

previously collected water-level data. 

Three field crews deployed static GNSS receivers over 

16 reference marks colocated with active and discontinued 

water-level streamgages throughout Rainy River, Rainy Lake, 

Namakan Reservoir, and select tributaries of Rainy Lake 

and Namakan Reservoir. A static GNSS receiver also was 

deployed over a National Geodetic Survey cooperative base 

network control station that was used as a quality-control 

reference mark, resulting in a total of 17 surveyed reference 

marks in this study. Satellite data were collected simultaneously during a 5-day period and processed independently by 

the U.S. Geological Survey and Natural Resources Canada to 

obtain accurate positioning and elevations for the 17 reference 

marks. Deployment times for GNSS receivers ranged from 

29 to 68 hours, with a mean deployment time of 46 hours. 

Satellite data were processed using two different methods, and 

the results were compared as a measure of quality assurance. 

Results were similar between compared methods. Processed 

satellite data were used to convert published water levels to 

elevations referenced to the Canadian Vertical Datum of 2013 

in order to compare water-surface elevations in a uniform 

vertical datum throughout the study area. 

Offsets were applied to water-level data from surveyed 

streamgages to further evaluate the accuracy and utility of 

updated reference mark elevations presented in this study. 

In this report, an “offset” refers to the correction that needs 

to be applied to published data from a particular streamgage 

to produce elevation data referenced to a specified vertical 

datum. Daily mean water levels from active streamgages 

surveyed in this study were converted to water-surface elevations referenced to the Canadian Geodetic Vertical Datum of 

2013; graphical comparisons of water-surface elevations for 

streamgages in Namakan Reservoir, Rainy Lake, and selected 

rivers are presented. Active, permanent streamgages demonstrated strong hydrologic agreement throughout Namakan 

Reservoir, Rainy Lake, and surveyed river streamgages; 

water-surface elevations consistently decreased from upstream 

to downstream. Discontinued, temporary streamgages had 

more variability and less hydrologic agreement among 

water-surface elevations than active, permanent streamgages. 

Offsets presented in this report can be used in the evaluation 

of rule curves and in flood damage curves that fully assess the 

benefits of one regulation approach over another. In addition, 

offsets may be used to calibrate hydraulic models developed 

for four narrows that connect lakes of Namakan Reservoir, 

refine a digital elevation model, and support modeling studies 

designed to assess the effects of rule curves on aquatic vegetation, benthic invertebrates, northern pike, and walleye.

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18 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

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Appendixes 1–3
20 Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data

Appendix 1. Global Navigation Satellite System Data Collection Information 

Appendix 1 is available for download as an Excel® file at http://dx.doi.org/10.3133/sir20165109.

This appendix contains data collection information for the Global Navigation Satellite System (GNSS) as a Microsoft® 

Excel spreadsheet. The first worksheet (tab) in the spreadsheet is table 1–1, which provides a summary of collected satellite 

data for the 16 streamgage reference marks and the 1 National Geodetic Survey control station surveyed in this study. The other 

worksheets (tabs) in the spreadsheet contain the log files from the GNSS surveys for each of the reference marks and are presented in order of map number and are named according to the station numbers (table 1–1).

Table 1–1. Summary of collected satellite data for 16 streamgage reference marks and 1 National Geodetic Survey cooperative base 

network control station surveyed in this study.

Appendix 2. Processing of Raw Data Collected for 16 Streamgage Reference Marks and 1 National 

Geodetic Survey Cooperative Base Network Control Station Using Global Navigation Satellite 

Systems

Appendix 2 is available for download as an Excel® file at http://dx.doi.org/10.3133/sir20165109.

This appendix contains the data processing files collected for reference marks at the 16 streamgages and the National 

Geodetic Survey control station using Global Navigation Satellite Systems (GNSS) as a zipped file. The data were processed by 

Natural Resources Canada (NRCan) and the U.S. Geological Survey (USGS) using different methods. The zipped file contains a 

READ_ME file with information about the data processing files. The zipped file contains two folders (NRCan_Processing_Files 

and USGS_Processing_Files) for the processing file outputs from NRCan and the USGS, respectively.

Appendix 3. Surveyor Level Loop Information for Selected Sites

Appendix 3 is available for download as an Excel® file at http://dx.doi.org/10.3133/sir20165109.

This appendix contains surveyor level loop information as a Microsoft® Excel spreadsheet for the nine streamgage sites 

with reference marks that could not be surveyed directly using global navigation satellite systems. The first worksheet (tab) in 

the spreadsheet is titled “Read_Me” and provides a summary of the spreadsheet. The other worksheets (tabs) in the spreadsheet 

contain the surveyor level loop information for each of the nine sites and are presented in order of map number and are named 

according to the station numbers (see the “Introduction” section, table 1).

Publishing support provided by: 

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Minnesota Water Science Center

2280 Woodale Drive

Mounds View, Minnesota 55112

(763) 783–3100

Or visit the Minnesota Water Science Center Web site at: 

http://mn.water.usgs.gov/

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20165109

Ziegeweil and others—Network Global Navigation Satellite System Survey to Harmonize Water-Surface Elevation Data—Scientific Investigations Report 2016–5109