Best Satellite Image Source(s)

Roger EdrinnRoger Edrinn Global Mapper UserPosts: 721Trusted User
edited May 2010 in Raster Data
I need a source for Satellite photos of the earth and I know almost nothing about the subject. What I do know is how I plan to use the images for projects.

Project 1: Tracing land features
Inside Global Mapper, I would import geo-referenced images and trace visible land boundaries and features. I believe I need 10 meter accuracy, but again don't know what's possible. Also, are summer/winter images available, having snow on the ground could be useful?
An example: In Colorado irrigated crop lands have bounds, ditches, center-pivot irrigation systems, etc. I'd like to see all these and digitize them such that the rasters are now vectors.

Project 2: Raster to Vector conversion
It's possible to vectorize raster images for display inside vector only GPS receivers. I do not believe Global Mapper will do this. But my source of satellite images must allow this use w/o copyright issues.

How are satellite images purchased, all you can eat or per download? Let's say I need 1 x 1 mile per side images. Also, how big are the downloads?

Please clue the clueless or link me somewhere.

Thanks

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited November 2008
    Typical resolutions for imagery are 1m or better, so your 10m goal should be no problem. You can load your imagery into Global Mapper, either from your own data or using the File->Download Online Imagery tool, then use the Digitizer Tool to trace features over that data.

    There is a great tutorial on generating custom Garmin format maps using Global Mapper and the 3rd party tool cGPSMapper. See http://www.globalmapper.com/helpv10/cGPSMapper.pdf for this document.

    The only imagery that is built-in to Global Mapper that is not entirely free is the DigitalGlobe imagery accessible via the File->Download Online Imagery menu command. You can download watermarked imagery from DigitalGlobe for free, but if you want to export the imagery you would need to purchase access.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RalphieRalphie Global Mapper User Posts: 6
    edited November 2008
    Does it need to be satellite imagery? How big are the areas you want to analyze?
    If you are working with smaller areas, say a county at a time, get the NAIP data which is flown by the Department of Agriculture. They have orthorectified county mosaics that load quite nicely into Global Mapper.
  • Roger EdrinnRoger Edrinn Global Mapper User Posts: 721Trusted User
    edited November 2008
    So far I've opened the Digital Globe images w/ watermarks, those would work for the area and feature traces. For my second project, the watermark free images cost ~$5/sq-mile with the smallest bite of $500.

    Where do I get the Dept of Agriculture aerials?

    Thanks for the reply.
  • mikeqmikeq Global Mapper User Posts: 8
    edited March 2009
    You can get NAIP imagery at the usgs site. Simply use the viewer to zoom in on the area of interst and the NAIP imagery will show up under orthoimagery.

    The National Map Seamless Server Viewer
  • mikeqmikeq Global Mapper User Posts: 8
    edited March 2009
    You can also download directly into GM by adding the USGS WMS to the "Download Online Imagery/Topo/Terrain Map" selection located under the "File" menu. The USGS WMS address for NAIP imagery is...

    http://ims.cr.usgs.gov:80/wmsconnector/com.esri.wms.Esrimap/USGS_EDC_Ortho_NAIP
  • Roger EdrinnRoger Edrinn Global Mapper User Posts: 721Trusted User
    edited March 2010
    Just now getting back to this, some changes, some questions.

    The location for the imagery has just changed to:
    http://isse.cr.usgs.gov/arcgis/services/Combined/USGS_EDC_Ortho_NAIP/MapServer/WMSServer

    I created a very small bound and GM loaded that image in less than 5-min. But when I tried to zoom in GM appeared to be reloading the image. What is happening? How can I avoid this apparent reloading when I zoom?

    The images are awesome, I could see lightly used foot trails. Previously I loaded a county image, 500MB, took all day. Rather not download such big images, the GM load to screen is perfect.

    Thanks for any tips.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2010
    Online sources like this WMS server contain the data at many different zoom levels. Global Mapper always downloads the data at a zoom level appropriate for your current display. When you zoom in or out the data is re-downloaded at a resolution appropriate for the new zoom scale. Otherwise if you were zoomed out so that you were seeing the entire country the data would never finish downloading if it was coming in at full resolution!

    To fix your zoom at some scale, just export at the desired resolution to a new image file, then load that in rather than the dynamic online source.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger EdrinnRoger Edrinn Global Mapper User Posts: 721Trusted User
    edited March 2010
    To fix your zoom at some scale, just export at the desired resolution to a new image file, then load that in rather than the dynamic online source.
    Can I do this inside GM, or do I go to the seamless server and set the scale and bounds?

    Thanks
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2010
    There isn't any way to fix a download bounds for online sources when downloading them, instead just use an export, like the ECW export, to export to a new file at some fixed resolution, like say 1 meter in each direction. Then just unload the online source and load in the ECW file that you created.

    Note, I hadn't realized that the entire NAIP imagery data set was available through a WMS server. This is VERY cool, so I added it as a built-in source for everyone to use.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger EdrinnRoger Edrinn Global Mapper User Posts: 721Trusted User
    edited March 2010
    Bit surprised at the CPU time this takes. Looks like ~30 min to Export to ECW for roughly a 1-mi square at 1-meter. ECW is rasterizing vector data. I thought I already had a raster image.

    Never exported any rasters before, must be doing something wrong.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2010
    The time is almost certainly nearly completely the download time for pulling down the WMS server data at the export resolution, although this does seem excessive for such a small area. I am getting pretty fast access times for the NAIP data (i.e. screen fills even with my current slow Verizon 3G connection on my laptop are only about 15 seconds). Is your internet connection particularly slow?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger EdrinnRoger Edrinn Global Mapper User Posts: 721Trusted User
    edited March 2010
    The time is almost certainly nearly completely the download time for pulling down the WMS server data at the export resolution, although this does seem excessive for such a small area. I am getting pretty fast access times for the NAIP data (i.e. screen fills even with my current slow Verizon 3G connection on my laptop are only about 15 seconds). Is your internet connection particularly slow?
    That would be an understatement!!! I have roughly 2X of dial-up. I'm one of the 40% of rural America w/o broadband and little/no chance of getting it. When you live off the grid, their are sacrifices. Do have a Million Dollar view and no neighbors as compensation.

    Now I know.
  • DustyRobinsonDustyRobinson Global Mapper User Posts: 114Trusted User
    edited May 2010
    When using the NAIP WMS, is there a way to determine (or choose) what year the image is from?
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2010
    Not currently, the NAIP WMS server just has one NAIP layer as far as I know, and that just has whatever the latest is they have on their server.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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