**A New Circa-2000 Land Cover map of Northern Canada at 30-m Landsat
Resolution**

[I. Olthof, R. Latifovic and D. Pouliot]{.underline}

> **Abstract.** Previous northern land cover of Canada mapped within
> national or circumpolar products are too coarse thematically or
> spatially to address all emerging northern issues, including land use,
> wildlife and climate change. This paper presents the first 30m
> resolution land cover map of northern Canada designed to help managers
> and policymakers address these issues. Orthorectified circa-2000
> Landsat data from CTI Geogratis were acquired for Northern Canada from
> the treeline to the northern tip of Ellesmere Island and were combined
> into several radiometrically-balanced large-area mosaics. Literature
> on northern land cover and vegetation mapping as well as numerous
> northern vegetation surveys were examined to determine an optimal set
> of land cover classes to map and provide some reference information to
> assist class labelling. Field data gathered during numerous northern
> campaigns over the past few years were combined with land cover
> information from maps of protected areas generated by other government
> agencies such as Parks Canada, the Geological Survey of Canada and
> Territorial Governments to form a reference dataset for training and
> validation. The map will be made publicly available for download
> through Natural Resource Canada's Geogratis portal in 1:250k National
> Topographic System (NTS) mapsheets.

**Introduction**

Land cover is a fundamental land surface parameter that is most often
derived from remotely sensed imagery. In Canada, numerous national land
cover products have been generated from coarse-resolution (1-km) imagery
from the AVHRR and SPOT VEGETATION (VGT) sensors. Easy access to
Canada's southern landmass, a history of resource extraction and
experience interpreting satellite imagery have all contributed to
accurate and detailed land cover in southern Canada's developed
agriculture and forested regions. However, the absence of such factors
in northern Canada has led to overly generalized northern land cover in
previous national products.

Vegetation maps focussed on northern Canada (Gould et al., 2002) and the
circumpolar north (Walker et al., 2002) have been generated in recent
years that combine remotely-sensed image interpretation with expert
knowledge of the environmental controls on arctic plant distributions in
a GIS environment. These maps contain thematic detail not present in
national-level land cover products, but provide no greater spatial
detail because they are based on 1-km AVHRR imagery and ancillary data
at a coarse 1:7.5 M-scale. These maps are well-suited to the purposes
they were intended for, including numerous international efforts related
to global environmental change and education. However, certain
applications require more detail than these maps can provide, such as
wildlife conservation, resource development and carbon accounting for
climate change studies involving land use and land use change.

Detailed maps of certain regions in northern Canada have been produced,
including several northern Parks and protected areas. The knowledge that
is imbedded in these maps may be useful for extending land cover beyond
previously mapped regions to the whole of northern Canada. However,
since none rely on a common land cover legend, differences among class
definitions can lead to incompatible or inconsistent interpretation when
two or more land cover maps are extended over the same region. Thus,
differences need to be reconciled by defining a land cover type that
includes common features of both classes being mapped, or one of the
mapped classes should be considered in error.

In this paper, we use normalized 30m Landsat data from year circa-2000,
existing land cover products over of protected areas, site-level field
data, ancillary GIS data, literature on northern vegetation and northern
mapping and high resolution images from the Ikonos satellite to
interpret and map northern land cover of Canada at 30m resolution. This
product will provide the first thematic and spatially detailed coverage
of northern Canada that uses a common legend and is consistent in all
regions. Thus, all northern parks and protected areas now have access to
land cover information that allows managers to view each area
separately, or for the first time, different regions together in a
comparable fashion. Consistent radiometry on which the map is based as
well as a consistent legend now allow areas to be compared or combined
as needed.

**Satellite data**

Landsat data were processed by two groups and three different methods to
form the full coverage north of the treeline, as defined by Timoney et
al., 1992. A Baffin Island mosaic was created using the method by Gibson
and Nedelcu (2008), which uses multiple overlapping paths, a sensor and
satellite orbit model and few ground control points required to generate
georeferenced image products that are subsequently orthorectified. By
combining multiple paths of data and resampling once, clear-sky swaths
are obtained and original radiometry is preserved.

In addition, freely available orthorectified Landsat data covering
Canada north of the treeline were downloaded from the Centre for
Topographic Information (CTI) through the Geogratis portal, and the
University of Maryland through the Global Land Cover Facility (GLCF)
portal. Data were reprojected to the spatial reference and
radiometrically balanced using year-2000 SPOT VGT data (Latifovic et
al., 2004) following the procedure in Olthof et al. (2005). Other
large-area Landsat mosaics of northern islands, including Southampton
and islands in the Sverdrup basin, were generated using overlapping
areas between scenes and automated image matching procedures. Landsat
mosaics north of the coverage of VGT (72.25 degrees N) were normalized
using successive overlap areas with Landsat data located to the south to
produce consistent radiometry for the full coverage, which can be seen
in a 250m resampled version in Figure 1.

Sixteen individual radiometrically balanced 30m resolution large-area
mosaics were created of Landsat bands 3 (Red), 4 (Near Infrared; NIR)
and 5 (Shortwave Infrared; SWIR). Each mosaic was enhanced using a
common lookup table following the Enhancement Classification Method
(ECM; Beaubien et al., 1999) in order to compress the dynamic ranges of
water and clouds, snow and ice on the low and high end of the dynamic
ranges, respectively, while stretching the range representing land cover
to enhance the visual separability among classes. Enhanced images were
clustered to 200 spectral clusters using the Fuzzy K-means algorithm
(Bezdek, 1973) and a pseudo-colour table representing cluster means in
NIR, SWIR and Red displayed as Red, Green and Blue (RGB) was applied.

**Ancillary data**

Ancillary data were downloaded from the Alaska Geobotany Center's
Circumpolar Arctic Vegetation Map (CAVM) data page, including the
treeline (Timoney et al., 1992) and bioclimatic zones, which represent
biotic criteria that subdivide the arctic into units reflecting climatic
gradients (Edlund and Alt, 1989). Additional 1:50k data on water bodies
and elevation were downloaded from the Centre for Topographic
Information's (CTI) National Topographic Data Base (NTDB) through the
Geogratis web portal. The Geological map of Canada (Wheeler et al.,
1997) was used to stratify based on parent material. A map was generated
that combined bioclimatic zone, parent material and elevation into eight
different strata that were mapped separately. These strata were the same
as those used by other groups to map northern Canada and the circumpolar
north (Gould et al., 2002; Walker et al., 2002), as they have been
determined to control northern vegetation distributions at a global
scale. Bioclimatic zones three to five were mapped together due to a
lack of reference data for bioclimatic zones 1 and 2.

**Classification**

Each of the sixteen large-area cluster images were mosaiced into a 250m
coverage of the whole Canadian Arctic using Nearest Neighbour sampling.
Ancillary data were also gridded into the same coverage. This enabled
the creation of an overview product that could be treated synoptically,
instead of examining each large-area mosaic separately one at a time.
Classification and extensive visual quality checking was performed on
the resampled data before generating the full resolution product on the
sixteen mosaics (Figure 1).

![](media/image1.png){width="4.095833333333333in" height="3.025in"}

**Figure 1.** Landsat data for the Canadian Arctic north of the
treeline, bands 4, 5, 3 displayed as R, G, B.

A new, northern land cover legend was generated by examining 13 northern
vegetation legends and extracting common or compatible classes among
them. Four digital land cover maps were obtained for protected areas in
northern Canada, two of which were within bioclimate zone 5, and one in
each of zone 3 and 4 (Figure 2). A lookup table was generated to
transform existing land cover products to the common legend (Table 1).
Separate lookup tables were then generated that related the 200 spectral
clusters from the normalized Landsat

mosaic to classes from the common legend for each of the four land cover
products using a majority rule. A side-by-side examination of lookup
tables allowed the interpreter to check spectral clusters that have been
mapped to separate classes in each of the classifications. In addition
to the 250m resampled coverage used for quality checking, over each of
the four existing protected area classifications as well as three
additional regions where field data had been collected (Iqaluit,
Nunavut; Lupin, NWT; Tuktoyaktuk, NWT), classifications were generated
at full 30m resolution for visual assessment and quality control.

Because the four land cover classifications used to guide the labelling
of our product cover different bioclimatic zones and different regions,
spectral clusters should not necessarily represent the same land cover
class in each zone. This is also true where ambiguity exists in class
definition or where different interpreters view the land cover
differently. For clusters that span two or more zones, these differences
need to be reconciled so that they represent the same class at the
boundary between two zones. Failure to do this produces a discontinuous
land cover product between zones, such that zones are visible through
the class distribution in the final product.

To reconcile differences and similarities between zones, each zone was
buffered and the clusters that occurred frequently on each side of a
zone boundary were examined to ensure that they mapped to the same
class. Generally, a voting rule was used where disagreement existed
among classes assigned to spectral clusters in different lookup tables.
Experience interpreting land cover and available reference data were
also key in making decisions about cluster labelling (Figure 2). Those
clusters that occurred in adjacent zones but were not frequent along the
boundary were allowed to map to separate classes.

![](media/image2.wmf){width="5.625in" height="4.164583333333334in"}

**Figure 2.** Location of reference data used to assist in cluster
labelling.

  --------------- ---------------- ---------------- ------------ --------------- ------------ ------- ------------ ------------- -------- -------- -------- --------------
  Table 1.                                                                                                                                                  
  Association                                                                                                                                               
  among classes                                                                                                                                             
  in the digital                                                                                                                                            
  land cover maps                                                                                                                                           
  of protected                                                                                                                                              
  areas shown in                                                                                                                                            
  Figure 2, and                                                                                                                                             
  the common                                                                                                                                                
  legend used to                                                                                                                                            
  map northern                                                                                                                                              
  land cover.                                                                                                                                               

  Common legend                    Delta, GSC                    Yukon Coastal                                     Aulavik NP                               Tuktut NP
                                                                 Plain, EC                                                                                  

                                   Zone 5                        Zone 5                                            Zone 3                                   Zone 4

  **Graminoid**                                                                                                                                             

  1               tussock                                        10\. moist                                        11\. Hummock                             2\. tussock
                  graminoid tundra                               cottongrass                                       Tundra                                   tundra
                  (\< 25% dwarf                                  tussock                                                                                    
                  shrub)                                                                                                                                    

  2               wet sedge        7\. Grass /                   5\. wet         6\. wet              8\. moist    2\.                    6\.               1\. wet sedge
                                   Sedge                         graminoid or    graminoid,           tundra with  Depression             Slope             meadow
                                                                 wet bryophyte   low shrub            wet          Wet Sedge              Wet               
                                                                                                      inclusions   Meadow                 Sedge             
                                                                                                                                          Meadow            

  3               moist to dry     2\. Dry Tundra                9\. moist                                         7\. Sedge     8\.               9\.      3\. mesic
                  non-tussock      (willow-heath)                graminoid                                         Dominated Dry Mesic             Mesic    tundra
                  graminoid /      willow/sedge                  (non-tussock)                                     Tundra        Meadow            Meadow   
                  dwarf shrub                                                                                                    50%               70%      
                  tundra (50-70%                                                                                                                            
                  cover)                                                                                                                                    

  4               dry graminoid    1\. Dry Tundra                                                                  10\. Grass                               5\. dry tundra
                  prostrate dwarf  (sedge-heath)                                                                   Dominated Dry                            
                  shrub tundra                                                                                     Tundra                                   
                  (70-100% cover)                                                                                                                           

  **Shrub**                                                                                                                                                 

  5               low shrub (\<                                  11\. low shrub                                                                             4\. shrub
                  40cm; \> 25%                                   tundra                                                                                     tundra
                  cover)                                                                                                                                    

  6               tall shrub (\>   12\. Tall Willow              12\. shrub                                                                                 
                  40cm; \> 25%     & Alder (dense                thicket                                                                                    
                  cover)           cover)                                                                                                                   

  7               prostrate dwarf                                13\. dry dryas                                    4\.                                      
                  shrub                                          tundra                                            Successonal                              
                                                                                                                   Dry Tundra                               

  **Sparse                                                                                                                                                  
  vegetation**                                                                                                                                              

  8               sparsely                                                                                                                                  
                  vegetated                                                                                                                                 
                  bedrock (2-10%                                                                                                                            
                  cover)                                                                                                                                    

  9               sparsely                                       14\. dry                                          5\. Stoney                               7\. rocky
                  vegetated                                      partially                                         Sandy Barren                             barrens
                  till-colluvium                                 vegetated or                                                                               
                  (2-10% cover)                                  barren                                                                                     

  10              bare soil with                                                                                                                            6\. sparsely
                  cryptogam                                                                                                                                 vegetated
                  crust - frost                                                                                                                             ground
                  boils                                                                                                                                     

  **Wetlands**                                                                                                                                              

  11              wetlands         3\. Wetlands     6\.          4\. aquatic                                                                                
                                                    Intertidal   tundra                                                                                     

                                                                                                                                                            

  12              barren           11\. Beach /                  7\. wet barrens                                   1\. Bare                                 9\. sand and
                                   Bare Soil                                                                       Ground                                   gravel

  13              ice / snow                                     1\. ice                                           13\. Snow and                            11\. snow and
                                                                                                                   Ice                                      ice

  14              shadow           5\. Cloud                     15\. mountain                                     12\. Clouds                              13\. cloud and
                                                                 or cloud                                          and Shadows                              shadow
                                                                 shadows                                                                                    

  15              water            10\. Clear Water 8\. Turbid   2\. clear water              3\.                  3\. Water                                10\. water
                                                    Water                                     silty                                                         
                                                                                              water                                                         
  --------------- ---------------- ---------------- ------------ --------------- ------------ ------- ------------ ------------- -------- -------- -------- --------------

The Classification by Progressive Generalization (CPG) (Cihlar et al.,
1998) approach was used in a last step with the pre-determined lookup
tables used as a guide for final cluster merging and labelling. The CPG
method is then used to merge clusters based on spectral similarity and
spatial proximity to generalize in a series of steps from the 200
cluster image to the final classification product. Visual quality checks
are key at each generalization step, and are performed by applying a
pseudo-colour table generated from the enhanced spectral bands and
comparing the resulting image to the previous generalization step to
ensure no loss of relevant land cover information. The overall goal is
to preserve shapes and features in the land cover classification that
are present in the original imagery. Lookup tables were checked to
ensure that the semi-automated cluster merging as suggested by examining
multiple existing land cover products did not violate the principles of
the CPG method.

Once lookup tables were finalized and checked on the 250m resampled
product, they were applied to each of the sixteen 30m large area mosaics
under the appropriate stratum based on geology, bioclimatic zone and
elevation. NTDB water bodies were gridded and buffered to one pixel, and
clusters representing water beneath this water mask were assigned to the
water class. Topographic shadow was classified by assigning dark
spectral clusters not beneath the water mask to shadow in areas of high
relief based on the DEM. Three hundred and eighty 1:250k NTDB mapsheets
representing Canada north of the treeline were cut from the sixteen
large area classifications. A final quality check and manual editing was
performed on these sheets to remove sea and lake ice and fill in water
in no data areas representing open water (Figure 3).

![](media/image3.wmf){width="2.125in" height="1.2798611111111111in"}

**Figure 3.** Three hundred and eighty 1:250k NTDB land cover tiles
mosaiced at 250m spatial resolution forming the land cover of Canada
north of the treeline.

**Validation**

To date, minimal validation has been performed on the final product
considering its vast coverage. For three areas where field data were
collected, per pixel accuracy assessments were performed (Table 2).
Additional reference data has is being continuously added to the
reference database shown in Figure 2, which should provide sufficient
data to do a proper validation in the future. In addition to a limited
per pixel accuracy assessment, agreement between the final product and
CAVM was assessed by examining the resampled 250m land cover
distribution within each CAVM class. CAVM can be considered as a
standard on the circumpolar artic vegetation distribution at a broad
scale due to the rich information imbedded in this map stemming from
extensive northern experience of the primary investigators. However,
CAVM classes represent plant communities, while Landsat classes tend
more towards growth form and less towards communities. Thus, CAVM lacks
the finer scale detail present in the current map. Nonetheless, a
comparison between these maps is informative to see if the broad scale
variation in CAVM is present in our Landsat classification.

  ---------------------- ------------------ ----------- ------------------
  Table 2. Per pixel                                    
  overall accuracy for a                                
  limited field samples                                 
  collected in                                          
  Bioclimatic zones 4                                   
  and 5.                                                

  Region                 Bioclimatic zone   N           Overall accuracy

  Iqaluit, Nunavut       4                  46          84.7%

  Lupin, NWT             5                  23          78.3%

  Tuktoyaktuk, NWT       5                  7           71.4%
  ---------------------- ------------------ ----------- ------------------

A matrix showing the Landsat land cover distribution beneath each of the
CAVM vegetation community classes is presented in Table 3. Only Landsat
classes contributing ten percent or more to the CAVM class are shown for
clarity. Careful examination of this matrix reveals a high level of
agreement between these maps. For example, the CAVM low-shrub tundra
class is composed of 23% tussock graminoid tundra (with less than 25%
dwarf shrub), 23% low shrub (less than 40cm tall), and 9% tall shrub
(more than 40cm tall), in total accounting for 74% of the CAVM class. A
breakdown of all CAVM classes is beyond this discussion, but all CAVM
classes can be understood in terms of their composition as determined by
Landsat.

  ------------------------- ----------- -------- ------------- ----------- -------- -------- ----------- ----------- ---------------- ----------- ---------- -------- -------- -------- -------- --------
  Table 3. Distribution of                                                                                                                                                                       
  Landsat land cover within                                                                                                                                                                      
  each Circumpolar Arctic                                                                                                                                                                        
  Vegetation Map (CAVM)                                                                                                                                                                          
  class.                                                                                                                                                                                         

  **Landsat class**         1           2        3             4           5        6        7           8           9                10          11         12       13       14       15       

  **CAVM class**            tussock     wet      moist to dry  dry         low      tall     prostrate   sparsely    sparsely         bare soil   wetlands   barren   ice /    shadow   water    Total %
                            graminoid   sedge    non-tussock   graminoid   shrub    shrub    dwarf shrub vegetated   vegetated        with                            snow                       
                            tundra (\<           graminoid /   prostrate   (\<      (\>                  bedrock     till-colluvium   cryptogam                                                  
                            25% dwarf            dwarf shrub   dwarf shrub 40cm; \> 40cm; \>             (2-10%      (2-10% cover)    crust -                                                    
                            shrub)               tundra        tundra      25%      25%                  cover)                       frost boils                                                
                                                                           cover)   cover)                                                                                                       

  Cryptogam, herb barren                                                                                             **22**                                  **45**                              **67**

  Rush/grass, forb,                                                                                      **14**      **19**           **14**                 **12**                              **59**
  cryptogam tundra                                                                                                                                                                               

  Cryptogam barren complex                                                                   **10**      **53**                                                                         **11**   **74**
  (bedrock)                                                                                                                                                                                      

  Prostrate dwarf-shrub,                                                                                             **20**           **15**                 **19**                     **10**   **63**
  herb tundra                                                                                                                                                                                    

  Graminoid, prostrate      **11**      **12**                                               **11**                                   **17**                                            **10**   **62**
  dwarf-shrub, forb tundra                                                                                                                                                                       

  Prostrate/Hemiprostrate                                                                    **10**      **46**                                                                         **10**   **66**
  dwarf-shrub tundra                                                                                                                                                                             

  Nontussock sedge,         **10**      **10**                             **10**            **13**      **13**                                                                         **13**   **68**
  dwarf-shrub, moss tundra                                                                                                                                                                       

  Tussock-sedge,            **20**                                         **14**            **17**                                                                                     **13**   **64**
  dwarf-shrub, moss tundra                                                                                                                                                                       

  Erect dwarf-shrub tundra  **13**                                                           **19**      **13**                                                                         **17**   **62**

  Low-shrub tundra          **23**                                         **23**   **9**                                                                                               **18**   **74**

  Sedge/grass, moss wetland **10**      **13**                                               **11**                  **10**           **14**                                            **14**   **71**

  Sedge, moss, dwarf-shrub              **24**   **10**                                                                                                                                 **13**   **47**
  wetland                                                                                                                                                                                        

  Sedge, moss, low-shrub    **11**                                         **11**            **12**                                               **12**                                **24**   **71**
  wetland                                                                                                                                                                                        

  Noncarbonate mountain                                                                                  **26**      **14**                                  **15**                              **55**
  complex                                                                                                                                                                                        

  Carbonate mountain                                                                                                 **22**                                  **20**            **13**            **55**
  complex                                                                                                                                                                                        

  Nunatak complex                                                                                                                                            **22**   **44**   **11**            **76**

  Glaciers                                                                                                                                                            **75**   **10**            **85**

  Water                                                                                                                                                                                 **87**   **87**

  Lagoon                                                                                                             **8**                                                              **72**   **80**
  ------------------------- ----------- -------- ------------- ----------- -------- -------- ----------- ----------- ---------------- ----------- ---------- -------- -------- -------- -------- --------

**Acknowledgements**

We would like to acknowledge Robert McGregor and Stefan Nedelcu for
their contributions in processing Landsat data for several islands in
the high Arctic under the Secure Canadian Energy Supply Program,
Hydrocarbon Potential of the Arctic Project. We also gratefully
acknowledge Dr. Frank Ahern for his comments.

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