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I have a grid (in .img format) with pixel values ranging from -10,000 to 10,000, which i would like to contour. but i would like to contour only -3000 to 0 range. is this possible to set this up during contouring? or is there a way i can restrict the raster grid to display only -3000 to 0 before i start contouring?

Using Arc 9.3.1, with one extension (spatial analyst), nothing else.

  • Did you rule out SetNull to set all the values greater than 0 to nodata? I don't have the 9.3 help files here, so you will have to check the exact syntax for your system. – user681 Feb 23 '12 at 12:09
  • @Dan, thanks for that. this is simple yet effective way, exactly what i wanted. – gleeks Feb 28 '12 at 1:13
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You can also use the Contour List tool if you have access to Spatial Analyst ( http://webhelp.esri.com/arcgiSDEsktop/9.3/index.cfm?TopicName=Contour_List ) or 3D Analyst ( http://webhelp.esri.com/arcgiSDEsktop/9.3/index.cfm?TopicName=contour_list_(3D_Analyst) ) These let you specify custom intervals for your contours, so you can simply use -3000 as your first value and 0 as your last value and then set the values in between to whatever intervals you want.

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You can use 'Contour with Barriers' tool from Surface toolset. To specify a range you have to create text file with a line of values:

-3000 0 A B

where A is contour interval and B is indexed contour. The path to this file should be specified in 'File Containing Contour Value Specifications' field.

For example for values:

-3000 0 500 0

a polyline layer will be created with contour interval 500.

You can find more information in the tool help.

  • Just to be clear: is it the case that you are not proposing using any barriers at all, but just suggesting this tool because it (almost incidentally) allows user-specified limits on the contour range? (There's nothing the matter with that; I think it's a clever solution.) – whuber Feb 23 '12 at 15:40
  • @whuber I mentioned this tool as it's flexible and generic. And of course in this case there're no barriers. 'Contour List' tool is also ok when one has to type only several contour values (but it has no option to specify interval). – Marcin Feb 24 '12 at 7:28
  • thanks, marcin. this is very useful, especially if i have a few sets of contouring range with diff intervals to run in a single grid. – gleeks Feb 28 '12 at 1:18

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