How to interpolate and multiply layers using Global Mapper or ArcGIS

fadifadi Global Mapper UserPosts: 7
edited June 2010 in Raster Data
Hi All,
Kindly, I have a mean annual rainfall data of twenty meteorological stations with its lat long coordinates. Also I have the NDVI fraction image and I have already converted it into an ESRI shape file.
Now, could anyone please let me know: 1- How I can interpolate those rainfall data into one raster or vector file using Global Mapper or ArcGIS at first, then 2- How I can make a new layer (in Global Mapper or ArcGIS) by multiply the rainfall data layer by the NDVI layer in order to get a new layer representing the result of the multiplying of those two layers. 3- How I can classify the new resultant layer into five classes.
Many thanks in advance.
Best regards.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    I think first you'll want to create an "elevation" grid from your mean annual rainfall points. To do this first make whatever attribute of your points has the rainfall be treated as the "elevation" attribute on the Options dialog for the layer accessible from the Control Center. Then right-click on the layer in the Control Center and select the option to create an elevation grid from the layer. This will give you an interpolated grid with the rainfall values (they'll be treated as elevation values).

    Is your NDVI layer coming in as an elevation grid as well? If so you can combine it with your just created rainfall layer using the File->Combine Terrains menu command, although currently multiplying the values isn't an available operation (this can easily be added though).

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fadifadi Global Mapper User Posts: 7
    edited May 2010
    Dear Mike, many thanks for your concern. In fact NDVI layer is in Erdas imageine (img) format, so please what I have to do? best regards.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    Does your NDVI layer come in as an elevation Erdas Imagine file or just a raster image?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fadifadi Global Mapper User Posts: 7
    edited May 2010
    Dear Mike, my NDVI layer is a raster image. Thanks a lot for you.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    There isn't any way in Global Mapper to use a raster image for gridded operations. You have to have your NDVI data as a gridded data set in order to do anything other than just visualize it.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fadifadi Global Mapper User Posts: 7
    edited May 2010
    So please Mike could you tell me how can I convert it into a gridded data. best regards.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    Unfortunately there really isn't a way to convert a raster image into a gridded "elevation" file with useful values as you just have a picture. Do you have the NDVI data in any other form, like perhaps as area boundaries for the different values, that you could use to generate a gridded data set?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fadifadi Global Mapper User Posts: 7
    edited May 2010
    Yes, I have the NDVI layer in an ESRI shape file, as well as to a second point shape file that represents the meteorological stations in the study area. As I said before I need to interpolate the point layer into a new layer then multiply that layer by the first layer (NDVI shape file). Then I have to classify the resultant layer into 5 classes. So, kindly is that possible to do by Global Mapper, if so, how can I perform it? Thanks a lot again mike for your concern.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    Does your NDVI Shapefile data have some kind of attribute with the value that you want to multiply by? If so you can load the Shapefile, setup that attribute to be the "elevation" attribute on the Options dialog for the layer, then right-click on the layer in the Control Center and select the option to create an elevation grid from the layer. Then you can combine that with the grid created from your point layer with a multiplication operation to get your desired result.

    Note that I have just added Multiply as an available combine operation, so you will need a new build to have that available. I have placed a new build at http://www.globalmapper.com/global_mapper11.zip with the change for you to try. Simply download that file and extract the contents into your existing v11.xx installation folder to give it a try. If you are using the 64-bit version, there is a new build available at http://www.globalmapper.com/global_mapper11_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fadifadi Global Mapper User Posts: 7
    edited June 2010
    Thanks a lot Mike, I will have a try and then I will tell the results. Thanks again!
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