scaling raster images in Surfer

sgustemssgustems Global Mapper UserPosts: 3
edited July 2010 in Raster Data
Hi,

I have been downloading orthoimagry for the last couple of years from the EPA seamless web page for use as basemaps in surfer. I have attempted to download orthoimagry in GM because it's much quicker. When I use the GM downloaded images as a basemap in Surfer, I can't seem to scale the images. Is there a difference between the file types? What could cause the scaling issue?

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    What exactly do you mean when you say you can't scale the images? When you pull the data into GM, what format are you exporting as to use in Surfer and what resolution are you exporting at?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • sgustemssgustems Global Mapper User Posts: 3
    edited July 2010
    Mike, The projection of the orthophoto is shown as geographic WGS84, ARC Degrees. I'm exporting raster data as PNG files. I select 24-bit RBG and export "all visable data on screen". I don't change anything else. When I import the GM exported PNG files in to Surfer as a basemap, I click on the XY grid and select scale tab. I select porportional XY scaling and select a scale that I think will work for my page size. Problem is that the map units that the images imports in is so small (1" = 0.0018426389 map units). when I try to changes the map units to 100 (for 1" = 100') the page length drops to zero. I'm hoping this is someting to do with the projection or file type. When I export the Orthos from seamless.gov and use as a basemap; no problem.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2010
    It sounds like Surfer isn't dynamically reprojecting the data but just assuming it is in linear units. Try setting your projection to UTM on the Projection tab of the Configuration dialog prior to exporting so you can get linear units (like meters or feet) for the output file and see if that scales properly.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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