Posted on September 2nd, 2014

Comparing 40-cm and 50-cm GeoEye-1 and WorldView-2 Imagery

WV2_DenverMetro_40vs50cm_4_13_2012_I
WV2_DenverMetro_40vs50cm_4_13_2012_IIHere are two comparisons of 40-cm and 50-cm resolution WorldView-2 data collected over the Denver, Colorado metropolitan area on April 13, 2012. The GSD of these WV2 images is 46.4 cm. You will see that while the spatial extent changes from the 40-cm to the 50-cm tile, the center of the images remain unchanged. (Images Courtesy: DigitalGlobe)

GE1_DenverMetro_40vs50cm_8_25_2011_I
GE1_DenverMetro_40vs50cm_8_25_2011_IIHere are two comparisons of 40-cm and 50-cm resolution GeoEye-1 data collected over the Denver, Colorado metropolitan area on August 25, 2011. The GSD of these GE1 images is 41.4 cm. You will see that while the spatial extent changes from the 40-cm to the 50-cm tile, the center of the images remain unchanged. (Images Courtesy: DigitalGlobe)

Now that the US government has lifted the 50-centimeter (cm) resolution restriction on satellite imagery, it is time to compare 40-cm and 50-cm samples of GeoEye-1 (GE1) and WorldView-2 (WV2) data. In order to do this, we selected extremely low off-nadir GE1 and WV2 data collected over the Denver, Colorado metropolitan area and ordered each in 40-cm and 50-cm resolution. A matching color balance was then applied to each of the 40-cm and 50-cm datasets and animated GIFs were created to show the two images ‘side-by-side’.

Here are our thoughts about the comparison of 40-cm and 50-cm GeoEye-1 and WorldView-2 images:

  • It is clear that 40-cm resolution matters with regards to the level of detail you can see and the maximum zoom (or map scale) possible with these images. However, it is unclear if you can actually see smaller features in 40-cm imagery than were visible in 50-cm imagery.
  • Features at the edge of the detection limits in 50-cm imagery can now be discerned and identified with a higher level of confidence.
  • However, all this said, there is only a portion of the GE1 and WV2 archive that should be produced at 40-cm resolution as imagery collected with a ground sampling distance (GSD) equal to or larger than 50-cm would make little sense to produce at a lower resolution. And similarly, in most cases, it would make little sense to produce an image with 49-cm ground sampling distance at 40-cm resolution and so on and so forth.
  • Now let’s formalize the statement above with some statistics. In our eyes, only imagery with less than 45-cm GSD for GE1 and then 48-cm GSD for WV2 makes sense to produce at 40-cm resolution given the soon to be higher price for this data; but these cut-offs are obviously subject to the specific needs of your project.  To this end, here is a breakdown of the GE1 and WV2 2014 archive (as of August 20th) by ground sampling distance.
    • GE1
      • Greater than or equal to 50-cm GSD – 39.9%
      • Less than 50-cm and greater than or equal to 45-cm GSD – 38.2%
      • Less than 45-cm GSD – 21.9%
    • WV2
      • Greater than or equal to 50-cm GSD – 78.9%
      • Less than 50-cm and greater than or equal to 48-cm GSD – 13.2%
      • Less than 48-cm GSD – 7.9%

    If you have any questions about the images in this article or the changes in available resolution for GE1 and WV2, please send us an email at sales@apollomapping.com.

    We are also happy to share the raw JPEGs used to create these animated GIFs if that would be an easier comparison for you, just send us an email to get them!

    The Apollo Mapping sales team is curious what you think about these 40-cm versus 50-cm GE1 and WV2 images? If you have some feedback, feel free to leave us a post below!

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