U.S. Department of the Interior

U.S. Geological Survey

Progress and Plans 

for Processing

Airborne Data

Philip A. Davis

GCMRC
Primary Objectives

1. Provide consistent, calibrated, and undistorted multispectral image

and DSM databases for the Colorado River corridor from Lake Powell to 

Pierce Ferry every 4 years. Image data at 20-cm resolution, DSM data

at 1-m resolution, and both with 30-cm positional accuracy.

2. Analyze these periodic databases to examine periodic changes

in sandbars, campsites, vegetation, geomorphology, and near-shore

aquatic habitats as a function of dam operations.

Status: We are now collecting the best data possible. Although

we got behind schedule in providing the final databases for various

scientific analyses, we are rapidly catching up and will complete

all databases before the 2013 data are delivered this year.
Historical Perspective

Before 2002, we collected aerial photography annually at a cost of

about $45,000/annum, but the data were not rectified or calibrated,

few people used the film, and rectification was estimated to cost

$500,000/annum in 2002.

We started using digital cameras in 2002 every 4 years with the 

contractor rectifying and mosaicking the imagery in 2002 and 2005

at a cost of $250,000-$300,000/annum, but the contractors’ image

products had several flaws, which caused serious problems and 

time in analyzing the imagery.

In 2009 (and 2013) we employed a new sensor ($433,000) and the 

contractor delivered just the rectified flightlines, which we then select the

best flightline segment, calibrate the flightlines for consistency, 

and create the image mosaics. The resulting imagery has been

significantly easier and faster to process by a time factor of 7. The

final 2009 image database is the best in existence for the corridor.
East flightline with scarp smearing

West flightline without smearing
N

0 50 METERS

0 100 FEET

Prevalent Surface Smear Effect

West flightline without smearing

East flightline with smearing
The 2009 imagery are far superior to 2002 or 2005

for all canyon resource mapping and assessment -

sandbar example shown by the next sequence of slides.
0 20 METERS

0 100 FEET

N

RM 30.7 - 2002
0 20 METERS

0 100 FEET

N

RM 30.7 - 2005
0 20 METERS

0 100 FEET

N

RM 30.7 - 2009
The 2009 imagery are also superior to 2002 or 2005

for detailed vegetation mapping and assessment
RM 67.5 - 2009

Common canyon 

vegetation species are 

quite distinct on the 2009 

imagery, not so bad on the 

2002 imagery, and less so 

for 2005.
So have the data been used that were 

acquired in 2002, 2005, and 2009?

I have provided a document from Tom Gushue (our GIS guy) outlining

the uses that have been made, to his knowledge, of the airborne

data since 2002 (Justification for Remote Sensing Overflight Data.docx). 

Granted, not all of the uses are scientifically tangible in that the use alone

does not directly address AMWG issues, but most of the uses of the data

have greatly assisted and improved scientific data collection and/or analyses.

In the spreadsheet that I provided is a list of the conference presentations or

publications that have used the airborne data in their analysis and/or

interpretations, but I do not always know when the data are used and 

by whom, since it can be obtained directly from our data servers.

“Yes, Phil, but how has the data been used to address the systemwide issues

that can only be approached with such data?”
Systemwide Data Analysis Update

There are 3 systemwide tasks for the remote sensing data.

1. Provide gross vegetation cover and a classified vegetation databases.

2. Provide landcover for 1,200 sandbar and campsite areas that consist of

water, gross vegetation, sand, other smooth material, and rough

material (some of these units could be also used by aeolian studies).

3. Number 2, but for entire surface up to 250,000 cfs for possible stagedischarge, climate, and mass-movement effects. This database

would also include aspects related to fish habitat that is not

considered in item 2, such as backwater areas, cobble bars,

and debris flows.

No. 3 presents more ambiguity in the results and difficulty in the approach

than does no. 2, due to the larger variety of surface materials upslope, thus

The final approach for no. 2 will be made more rigorous for no. 3.
Vegetation

The gross vegetation databases for 2002, 2005, and 2009 are completed.

The 2002 vegetation has been classified; the 2009 vegetation is being classified

by a UA PhD student as part of her thesis.

The 2005 imagery has some serious surface smearing, which obscures 

vegetation in places. We need to create exclusion areas for that

database so that its analysis does not consider these “voids.”

Once 2005 exclusion areas are established (before June), the gross vegetation

changes can be easily analyzed, but we currently lack a botanist with

canyon experience to interpret the results.

The following is an example of some analyses taking place.
RM 41 Campsite Vegetation Change 2009-2002

Camp + -

No 

Change

Upper Buck 

Farm

15 % 3 % 82 %

Buck Farm 10 % 3 % 87 %

Below Buck 

Farm

47 % 2 % 51 %

Lopers 51 % 0 % 48 %

Increase

Decrease

Change 2002-2009
Sandbar and Campsite Analyses

The analysis for this task is conducted in 2 stages.

The first stage takes the water, vegetation, and bare-ground mask, further

Refines water and sparse vegetation units, segments the remaining bareground unit into four brightness levels based on image statistics, filters the 

image data to reduce local noise, forms surface texture, and several other 

steps. This stage is completed for 2002 and 2009.

The second stage employs a spectral, textural, and spatial contextual analysis on

the two brightest bare-ground units (and may go down one more unit if wet sand

exists in the darker unit). At this point, the last step in the analysis for wet sand

needs to be designed and tested (it is the most difficult). The complete analysis

for 2002 and 2009 will be completed before June. When the stage 2 algorithm

Works at 90% or better accuracy, each of the 1,200 areas requires 1 minute

to process.

The following slides show an example at RM 195. The sand and vegetation units

will be vectorized and provided to the scientists for spatiotemporal analyses.
2002 CIR image
2002

Phase 1 Product
2002

Phase 2 Product –

last step needed to

separate wet sand

within yellow unit.
2009 CIR image
2009

Phase 1 Product
2009

Phase 2 Product –

last step needed to

separate wet sand

within yellow unit.
2002

Phase 2 Product –

last step needed to

separate wet sand

within yellow unit.
Full Canyon Geomorphic Analysis

The computer-generated surface units will be completed and published as

a Data Series before the 2013 data are delivered. I need to interface with

fish scientists to ensure they get what they need. Parts of the database 

require visual geomorphic mapping using the 2009 imagery and altering the

units for the 2002 imagery where change has occurred. Once mapped, 

geomorphic unit alteration for subsequent years is rapid, just has not been

done canyonwide.
2002 and 2009 DSM Data

I have fully assessed the accuracy and precision of these systemwide

topographic databases. Summary of observations:

1. Vertical accuracy for 2002 = 28 cm, 2009 = 26 cm

2. Vertical precision between 2002 and 2009 = 13 cm

3. Each dataset has vertical offsets and these do vary throughout

the corridor, which I can correct.

4. There is some co-registration issues, which I will also correct, to make

change detection for accurate.

5. Once calibrated the data will be sufficiently precise for examining 

canyonwide changes for certain resources (maybe not for cultural

features) and will be very easy to detect mass movements, which I

have observed between the data sets (which in the past we only

detected by visual examination of 2,500 air photos).
by June

Working on final step in twophase image analysis to 

provide landcover databases 

for sandbar and campsite 

analyses using 2002 and 2009 

data.

Will have the 2002 and 2009 

data required for corridorwide sandbar and campsite 

change detection within 

1,200 sites.

Will have published naturalcolor and color-infrared 

imagery from 2009 as a Data 

Series so it is available on the 

USGS publications site.

USGS Data Series

by August

Will have the 2002 and 2009 

DSM data calibrated and will 

start determine its use for 

coarse- and fine-grained 

sediment studies.

USGS Data Series

by Oct

Will have above data for entire 

corridor augmented with 

manual geomorphic units 

(debris fans, bedrock, cobble 

bars, etc.) and publish 

databases as Data Series

USGS Data Series for 2002 and 2009

2013 Schedule