Spatial Analysis Based on Raster Data Processing - Introducing Geographic Information Systems with ArcGIS - page 496

Creating Rasters with Linear Features
We will create rasters for the line feature classes—Sewers, Streams, and Roads—in the same way as
above, with ArcToolbox. Actually, we don't have to load the feature class into ArcMap. Also, we can easily
set or check environment variables, important for determining the extent of a raster.
As mentioned, the extent of a vector dataset is pretty much determined by the data. However, raster
datasets are rectangles, and if you convert a vector dataset to raster, it is important to set the extents
to the same as other datasets of the study area. Since the soils feature class covers the entire study
area (and the sewers dataset, for example, does not), we earlier set the extent of rasters that we were to
create to that of the more extensive soils dataset. Below, we check just to make sure.
21. Start ArcMap with WC_Boat_Area_Map.mxd (Hints: Start ArcMap and find the map under
Existing Maps > Recent. Or, with the operating system, go to the folder WC_Boat_SA and
double-click the map entry.) Open ArcToolbox. You will use the Polyline to Raster tool. Where is
the tool in the ArcToolbox tree?
__________________ > _________________ > _______________.
Double-click the tool. In the Polyline to Raster window that opens, you find a text box for Input
Features. Browse to
___IGIS-Arc_ YourInitials \Spatial_Analyst_Data
\WC_Boat_SA\Wildcat_Boat_SA.mdb\Line_Features\Sewers
and click Add. For Field, choose DIAMETER. (You may recall that the two diameters were 45 and
60.) Browse to make the Output raster Sewers_rr2m in
___IGIS-Arc_ YourInitials \Spatial_Analyst_Data\WC_Boat_SA mdb\
For the Output Cell Size use 2.0. Do not OK the window yet.
22. Press the Environments button. Check that the Environment Settings are as you specified
earlier. If not, reset them, as described earlier. OK the Environment Settings window. OK the
Feature to Raster window. The raster Sewer_rr2m will show up in the T/C and the map.
23. Add the Sewers feature class, and make it a bright line of width 1. Make sure every other
layer is turned off except the two that relate to sewers. Zoom to the extent of the feature layer
Sewers. Look at it on top of Sewers_rr2m. Zoom way in on a place where the sewer lines
intersect. Note how a raster dataset represents lines. Use its attribute table to determine how
many cells it took to represent the 45-inch pipe. ________. The 60-inch pipe. ________.
24. Using the same approach as previously, make a raster of Streams, called Streams_rr2m.
For Field (which will become Value in the attribute table), pick STRM_CODE and use 2.0 again
for Output Cell Size. From the attribute table of Streams_rr2m, what are the two values that were
put in from STRM_CODE? ________, ________. (The Stream Code is an indicator of the size of
the stream.)
25. Use the same approach a third time to make Roads_rr2m, using RD_CODE.