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Dimitri


7,413 post(s)
#02-Dec-20 14:46

If you do GIS in the US, a great resource for free imagery in 1 meter or 0.6 meter resolution is the NAIP public imagery program, which does a surprisingly good job of covering most of the US every three years or so with four band (R,G,B and near infrared) imagery.

It can be a hassle downloading NAIP imagery from Earth Explorer and similar sites, so it's useful to be able to directly download NAIP files of interest from the USGS archives on Amazon AWS. Two new resources that will help:

1. Example: Create USGS File Names with Transform - A topic that explains NAIP file names and how to create an index of NAIP file name stems from published USGS indices. This also has great examples of using the new Transform workflow. Although this is a long topic for showing everything step by step, you can perform the whole thing on nationwide data in under ten minutes.

2. NAIP_file_name_grid.mxb - A new project published in the downloads pages for Viewer and Release 9 that provides the final, nationwide result of the transformations from the topic above, in a user friendly version for Viewer users. See the Read Me comments in that project for workflow tips.

If you like NAIP, get a bigger hard disk! :-)

PS: NAIP files on Amazon AWS are highly compressed in jp2 format, which is a slow format to import (Manifold uses a third party library, same as ECW). Once they're in a project and merged into a big image, you can save the project and it's off to the races. But they link very quickly. Also, when using jp2 you have to use the Style pane to switch them to using RGB.

Dimitri


7,413 post(s)
#02-Dec-20 15:33

Should have expanded that PS: a bit...

The quickest way to work with a bunch of NAIP files in jp2 form is to Link them into the project. I like to create a folder in the project, and then link an entire windows explorer folder of .jp2 files at once.

Next, in the main part of the project, create a map using Bing streets as a base.

Drag and drop all the linked images into the map.

Use the Merge Images tool to merge them all together into one image, using the Pseudo Mercator projection of the Bing layer as the projection for the result (luckily, the jp2 images use Pseudo Mercator, even though the jp2 format does not automatically georeference). If there are many to merge, do this over lunch or at night, as each .jp2 has to be decompressed in full to form the full resolution merged image.

Open the result and using Style set the channel arranger to RGB. You now have a big image that is a composite of all the linked images.

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