I am performing IDW interpolation. It gives a raster successfully with the correct values showing up in the contents table. However, the raster is not showing in the map area. On checking I found that the raster contains no data (when I tick the 'color the nodata' option in symbology , the whole interpolated area shows colored, indicating that the raster has no data. I don't understand what the problem could be.
I tried using text file as well as a sheet (excel) with 121 points. I even converted the sheet to shapefile and then tried to interpolate. Even then the raster output was empty.
Steps: Spatial Analtst Tools> Interpolation> IDW> dialogue box
In the dialogue, the settings are
Input point feature (text or excel sheet or shapefile)
Output cell size: 1.36359999e-03 (default)
Power: 2 (default)
Search radius: variable extent
Number of points 121
I suspect your data then.
Are the coordinates in decimal degrees?
What extent do they cover?
What are the Z values? Is there a range? or is it defined within the SHAPE field or as a separate field?
With "variable" the default number of points should be 12 not 121
Yes the data is in decimals.
Here are a point from the file
SiteNo. Code Lat Long 1 2 3 4 5 6
1 S-ARBG 34.0231 74.8129 148.00 141.00 140.00 142.00 142.00 143.00
I have 121 such lines in the file covering an extent between lat 33.8964 to 34.2373 and long 74.639 to 75.019
Yes. The deafult number was 12. I changed it to 121= number of points in the file.
Solved. There was an issue with the Mask being used in the Raster Analyis in Environments. I realised if the mask is a point or a line shapefile, the output interpolation raster is empty. The mask has to be a polygon shapefile, only then it will work.
...if your mask is a point feature class, then the output raster will only have values that coincide with the point locations (from the mask). That is why the legend had correct values.
Likewise for polylines.
Exactly. That's what was happening. When I was using line shapefile (boundary of the study area) as the mask, the output showed some color at the boundary only, and was empty inside.
Thank you Dan and Steve for the insight!