Procedure Library for Raster Error Analysis for line features

            The purpose of this procedure library is to get familiar with the process of Raster Error Analysis. Raster Error Analysis takes two separate shape files that include lines digitized from two different images of the same location, and determining the amount of difference or error between the two shape files.  Raster Error Analysis uses multiplication to combine two grid or raster files that have been given different values, so the product will be meaningful. In this case, the target file will have 1s where there are lines and 0s where there is no data. The warped file or the second file will have values given at the points, and then various distances radiating outward. When the two raster files are multiplied, any area with no data will still have 0 for the product, but any entity will have some distance associated with it.

 

Prepared by Andy Freed (freed@cc.wwu.edu) on March 5, 2001.

 

Required: ArcView GIS, Spatial Analyst Extension (See ESRI website)

 

Procedure:

1.     In ArcView, load the Spatial Analyst Extension from the File>Extensions menu.

2.     Add the two shape files that have the lines selected for distance analysis. (line1.shp, line2.shp)

Add “ones” field to Line1.

  1. Select the line1.shp theme and open the table by clicking on the table button
  2. Select Table>Start Editing, and Edit>Add Field.
  3. The new field will be called “ones” and will be a number field.
  4. Edit the values of the field “ones” so that every cell has a 1 in it.
  5. Select Edit>Stop Editing and save the changes.

Add Distance field around Line2.

  1. Select Line2.shp, and select Analysis>Find Distance.
  2. The output grid should be same as display. The Cell Size should be 10 meters. Hit Enter, then click OK. This process will take a while to complete.

Grid points & Ones.

  1. Select Line2 and select Theme>Convert To Grid.
  2. Select the location to save, and the name (GridLine1), click OK.
  3. The output should match the display, and the distance should match Line2. Hit Enter and click Ok.
  4. The Conversion Field is “ones”.
  5. When asked to join, click Yes.
  6. Click Yes to add the Grid to the View.

Reclassify the Grid points.

  1. Select GridLine1 and select Analysis>Reclassify
  2. Change the value of No Data to 0.
  3. Save the location and file name as reclassline1.

Map calculator.

1.     Select Analysis>Map Calculator.

2.     The equation should be ([Line 2 Distance ] x [reclassgrid1]).int and click Evaluate.

3.     Map Calculation 1 will show up, save it and its location to somewhere familiar. Save the file as a .dbf

4.     Select Analysis>Map Calculator.

Make the results available for Excel.

1.     Open Excel.

2.     Find the .dbf file you just saved from the map calculator.