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EarthExplorer - how to export vector shapefiles?

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#1
cityprints

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Hi,

 

I'm trying to export a vector shapefile from EarthExplorer to import into QGIS. I'm using EarthExplorer to create a selection around my area. I'm choosing DLG 1:100k under the Digital Line Graphs section for my dataset. Under the results tab, I'm clicking the Export Metadata button and downloading a shapefile for the area. 

 

The problem: The files downloaded are very small (like, 14k small) and when imported into QGIS, they are rendering as strange squares. I have attached screenshots. 

 

Does anyone know what I'm doing wrong?

 

Thanks for your time. 

Tony

Attached Files



#2
SteveR

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Dear Tony,

I'm going to assume you're interested in downloading hydrography for the Healdsburg CA 1:100,000 map sheet.  Here is how I'd do it.

1.  Search Criteria:
Address/Place:  healdsburg
Press the Show button
Select 1 Healdsburg, CA 95448, USA

2.  Data Sets:
Select DLG:100k

3.  Additional Criteria:
Select Hydrography
Select California

4.  Search Results:
Of the first 100 results, there are 10 results with Map Name=Healdsburg
First select the footprint to see the area.  The Healdsburg 100K map sheet has Lake Berryessa on the south end and Clear Lake on the north end.

Next, for each of the 10, press Download Options.
On my machine, I get a message something like, "You have chosen to open: 531083.HY.opt.gz"
Select Cancel and go on to the next.  The only ones you probably want are those that end in .HY.sdts.tar.gz.  There will be two of them, one for the east half of the sheet and the other for the west half.  You probably have to download both of them to determine which is which.  I'm no expert on this, and I don't know what OPT files are for.  I also don't know how to discover whether a file is OPT or SDTS without selecting it for potential download.

The GZ and TAR are two methods of compression.  Your software may be able to open it while still compressed.  If not, try to open it after each stage of decompression.  If your software can't directly open the SDTS format you may need to find some software to convert it to shapefile format. 

 

I don't have QGIS, but I suppose you know how to handle the files from there.

 

Earth Explorer is tricky to use, but it's a wonderful source of data, so don't let that stop you.

Steve Richardson
2i3D Stereo Imaging

 



#3
cityprints

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Hi Steve, 

 

Thanks so much for taking to type to respond. I'm afraid I'm still having difficulty, but it may be isolated to QGIS, not sure. 

 

I followed your steps and downloaded a file called 1425418.HY.sdts.tar.gz, which contained 37 DDF files. When I try importing these as a vector layer in QGIS, I get a message that the {file name} is not a valid or recognized data source. 

 

Basically, I'm looking to download all the roads for the area I'm selecting and shapes for the waterways (lakes, rivers, etc). The issue is that everything I download from EarthExplorer, I'm not able to open in QGIS. 

 

I understand that you don't use QGIS, so perhaps you can confirm I'm doing everything else correctly and I can troubleshoot QGIS directly?

 

Thanks again for your time Steve. 

Tony



#4
SteveR

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http://mcmcweb.er.us.../drc/dlgv32pro/

 

Dear Tony,

 

The above link will let you download a special version of Global Mapper which will easily open the SDTS.TAR.GZ files.  Once registered, I think it will let you save them as shapefiles as well. 

 

I'm not sure about that last statement because I just downloaded and registered it and haven't yet received my User Name and Registration Key.  Maybe somebody else in Cartotalk has done this and knows.

 

Steve

 

Okay.  Exploring the topic a bit further I found the following description of the software:

 

"The old USGS geodata viewer dlgv32 was the code foundation for the excellent Global Mapper data viewer and format converter. Global Mapper has granted the USGS a license to continue to release a feature-limited version of Global Mapper under the dlgv32 Pro name, primarily as a data viewer.The latest version of dlgv32 Pro was released a few weeks ago, and includes both 32-bit and 64-bit versions.


"The main limitations of dlgv32 are the inability to export data, and the limitation of four raster data files loaded at one time; you can get around this latter limitation by putting all the raster files into a single directory, and then using the File => Open All Files in a Directory Tree option. It has import support for virtually any vector and raster data format you can think of, as well as most projections/datums. There’s also access to online raster data sources, including high-resolution Digital Globe imagery (watermarked, with a daily quota), along with USGS topo maps and black-and-white ortho imagery. Additional features include GPS support, measurement tools, and data attribute query tools. The lack of any export capabilities (except perhaps by doing a screen capture), as well as no way to save a workspace, are big minuses, but it’s still worth a look."

http://freegeographytools.com/

 

This means DLGv32 Pro won't let you save the data, but it does a very good job of letting you view it.  In my opinion, if you've got $300 or so to spare, Global Mapper is a good investment.



#5
cityprints

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Thanks Steve. I'm on a MAC, so unfortunately Global Mapper isn't compatible. 

 

It seems that the universe doesn't want to cooperate. 

 

I'll keep working on it with QGIS. Thanks!



#6
SteveR

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http://converter.mygeodata.eu/

 

The above link is to a converter that will let you convert SDTS to shapefile online, probably even with your Apple system.  You zip the files and upload the zipped file, then download the shapefiles.  I zipped the 37 SDTS files together to get the result.  It only seems to be able to work with zipped files.  With the above hydro file I got back about 40 different shapefiles, but they all opened in the freeware Microdem, and so the process works.  With some experimenting you will probably be able to filter and merge them from there. 

 

Steve



#7
cityprints

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WOW! Great find Steve!

 

This is great, thanks so much for your help on this. I'm playing with it right now. 

 

Very excited!






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