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ajaysbharadwaj

Generate Contours and DEM from Google Earth

7 posts in this topic

Vitality of elevation information in the field of Geospatial technologies is a well known factor. This may be in the form of Spot Heights, Contours or DEM. Unfortunately the open source DEM we get is generally of spatial resolution of 30 meter and up. How many aware of the fact that the Elevation Information available in Google Earth can be utilized to get Spot Heights, Contours and DEM? Yes, the 3rd dimension information available in Google Earth can be manipulated to create Spot Heights, Contours and DEM in various GIS software using and small third party app. Below is the link for the tutorial to create Contours and DEM from Google Earth.

https://www.youtube.com/watch?v=237pVwC3fNk

 

Note:
Few people have asked me that altitude column is not getting updated. That is either problem with the installation or operating system. So try to re install tcx and try. Make sure that internet is connected then you do it. If it still doesn't work, try to do it in different operating system or different computer. Most of the people told it worked after doing this.

 

In the tutorial method is explained using SURFER to get final output. To do the process in ArcMap, follow the tutorial till getting excel file with elevation values, and then follow the other tutorial where it is explained how to create contours using spot heights (already available in the channel.)

 

Elevation information available in Google Earth is also interpolated values, so DEM or Contours extracted are as accurate as Google Earth Values.

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Thks for share this method for contour and DEM from Google Earth, is useful for all thks again and regards. 

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Sorry, but I don't understand the advantages over download the full SRTM data.

 

https://lta.cr.usgs.gov/SRTM

 

"SRTM 1 Arc-Second Global elevation data offer worldwide coverage of void filled data at a resolution of 1 arc-second (30 meters) and provide open distribution of this high-resolution global data set. 

Some tiles may still contain voids. Users should check the coverage map in EarthExplorer to verify if their area of interest is available.

Please note that tiles above 50° north and below 50° south latitude are sampled at a resolution of 2 arc-second by 1 arc-second."

 

You can donload fromUSGS's Eart Explorer http://earthexplorer.usgs.gov/

 

Data is also availabre from other sources, and in other formats

 

Cherrs 

 

Art

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yeah, google earth elevation data same with SRTM, you can download it for free

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For certain areas, elevation data doesn't come from SRTM. There are few other sources as well. Also the interpolation method used in GE looks better than the ones available in GIS software. However opinions may differ.

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ajaysbharadwaj

 

Nice issue do discuss! ;)

 

A) SOURCE DATA

yes, Google Earth uses mostly SRTM, but in someplaces uses other sources. 

We don't know where or the source quality, so.. we end with a DEM with unknow quality.

 

"NASA has released a void-filled version of the Shuttle Radar Topography Mission digital elevation model, known as "SRTM Plus" or SRTM NASA Version 3. SRTM Plus uses SRTM Version 2 (see below) where the radar interferometric method was successful (not void). Most voids are filled with elevation data from the ASTER GDEM2 (Global Digital Elevation Model Version 2)."

(see http://www2.jpl.nasa.gov/srtm/)

 

Bayond that, you can search in your Area of interest for better accuracy/Resolution DEMS

 

B) Interpolation

============

I strongly disagree with you.

 

You took grid data. get  XY points (manually), and then interpolate again to a grid!!!

 

Why don't you just use Shuttle Radar Topography Mission (SRTM) Data in Surfer??

(here go how: http://www.goldensoftware.com/Newsletter/issue52s# )

 

Contours "look better" because:

   1) you use less source data to interpolate

          (if you are use the more data points you are using interpolated points to interpolate,

           and if you use the same data ponits you work a lot more for the same results)

 

     and most important: 

   2) You interpolate with a smooth/stocatic method (Kriging), and using default parameters!

      You can use a lot of interpolation methods (In surfer, ArcGIS, or mostly any software)

      Linear, IDW, Krigin, NN, Spline, Trend, etc., with o without breaklines/barrers

       I ussually avoid use Kriging for terrian, beacuse tend to smoth terrian breaks. Why?

      ¡¡¡Nice and Smooth countous dosn't mean better acuracy!!! Ussually the oposite!

 

Regards

 

Art

Edited by Art409
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