3/6/2013 1 Advanced Geographic Information Systems Lab 8 Terrain Analysis http://bigthink.com/strange-maps Globalmapper.com Spatial Analyst extension ESRI controls sets of tools and offers them as extensions that you must acquire separate licenses for. You are licensed to use the Spatial Analyst toolset with your student edition software, but you must enable the extension before using it for the first time: From the Customize toolbar, choose Extensions… to open Extensions window. Check boxes next to all extensions (but especially Spatial Analyst) and click Close to enable licenses.
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3/6/2013
1
Advanced Geographic Information Systems
Lab 8 Terrain
Analysis
http://bigthink.com/strange-maps Globalmapper.com
Spatial Analyst extension ESRI controls sets of tools and offers them as extensions that you must acquire separate licenses for. You are licensed to use the Spatial Analyst toolset with your student edition software, but you must enable the extension before using it for the first time:
From the Customize toolbar, choose Extensions… to open Extensions window. Check boxes next to all extensions (but especially Spatial Analyst) and click Close to enable licenses.
3/6/2013
2
Question: What’s up with the
representative fraction love-fest?
Representative
fractions are so hip
and modern, just like
the slide rule and
abacus! They’ll never
become irrelevant.
1 : 2000 1 : 50,000 1 : 30,000
1 : 70,000 1 : 600
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1 : 3500 1 : 16000 Not True
Always True
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Lab 5 fine-tuning symbology
Which are the active polygons?
Semi-transparent fill demonstrates which polygons are active
Remove unnecessary layers to maintain focus on relevant data
OK:
Awesome:
Awkward to have irregular
values span multiple data
frames. Viewer has to
mentally isolate sections of
scale bar, do some
subtraction, visually
skootch things around…
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Lab 6 awesomeness:
Lab 6 awesomeness:
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Gridding on 30m DEM artifact of AGRC processing.
To get your hands on clean 30m DEM data retrieve directly from
USGS seamless server
Note:
Lab 8
Terrain Analysis Task 1 Define a Watershed Task 2 Stream order classification Task 3 Slope and curvature analyses Zonal Statistics as Table
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Lab 8 Task 1
Watershed delineation
How can we define a watershed using raster cell values representing elevation?
ArcGIS defines the watershed boundary by identifying cells with zero flow coming into them
Watershed Delineation:
How can we define a watershed using raster cell values representing elevation?
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Using Flow Accumulation to define watershed boundaries
3 1 0 0 1
2 1 0 0 1
2 1 0 0 1
2 1 0 0 1
3 1 0 0 1
2 0 0 0 1
5 2 1 0 0 1
2 1 0 0 1
3 1 0 0 1
Watershed Delineation:
Watershed Delineation:
Boundary is defined by the pour point.
Gsshawiki.com
Pour Point
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Lab 8 – watershed delineation
Lab 8 – watershed delineation
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Watershed Delineation:
DEM Fill Flow Direction (directional symbology or start over) Flow Accumulation (input flow direction) (integer) Naming convention: DEM10m_fd DEM10m_fa DEM10m_hs DEM10m_slp Slope hillshade_dem flowdir_dem Flow_Accumulation
Lab 8 Task 2
Flow accumulation
Stream order
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Flow Accumulation
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Lab 8 – stream orders • Provide table with
lengths of each order (units)
• In write up, defend reasonableness of stream network (include threshold value)
Where to lines of equal pressure go to relax?A. In ISO – bars (In Search Of isobars)
• Formal map: convince us watershed delineation was done correctly (compare to downloaded shapefile, compare [close up] to topo map)
• Write up: brief statement that convinces delineation was done
correctly (discuss/show screenshot and defend choice of pour point location?)
• Define tools
• Fill • Flow direction • Flow accumulation What does it mean (generally and what do output cell values represent [units?] and how does it calculate from elevation cell values?)
Lab 8 – Task 1
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Lab 8 – watershed delineation
Lab 8 – stream orders
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Discussion The lower the threshold value that was used, the more stream channel length that was created. Using a threshold value of 1250 created a total stream length of 245.94 km but using a threshold value of 1500 created a total stream length of 202.32 km. When the created drainage network was overlayed on top of a USGS topographic map there were a couple of differences:
streams were created that did not exist on the topo map; and, some created streams did not extend all the way in elevation as some of the streams from the topo map
The created drainage network will depend on:
• DEM resolution (quality) • pour point location • threshold value
Lab 8 – stream order
Lab 8 – surface analyses
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Lab 8 – surface analyses
• Provide captioned screenshots of Slope, PrC, PlC results
• Provide table with min, max, mean, and SD for slope, planform C, profile C (units!)
• Define tools:
• Zonal Statistics • Slope • Planform Curvature • Profile Curvature What do these mean, what do output cell values represent [units?], how are they calculated from elevation cell values?
Lab 8 – Task 3
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Planform Curvature Light cells - water flow is divergent Dark cells – water flow is convergent
Profile Curvature Light cells – water flow is decelerating Dark cells – water flow is accelerating