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How high?

Published in Engineering, Neogeography  |  3 Comments


Ever need to know the altitude at a given location on the Earth?

Well, there are several free resources to the rescue:

EarthTools has a webservice that covers the US and Europe using the SRTM data. Given a latitude/longitude it returns the height above sea-level in feet and meters. (found from Quakr Viewr)

Geonames offers two services using the SRTM data, and also the GTOPO30 from the USGS. Geonames gets bonus points for also returning the results in JSON. Geonames also uses a larger dataset – lands within 60 degrees north and 56 degrees south.

As “points” become rather ubiquitous among neogeographers/web-mappers, they’re moving into more complex geometries and especially 3D space. Having access to data means it is very easy to tie into services and applications. For example, making a hiking profile given just 2-d ground waypoints.

You can download the data yourself to do whatever you want with it. Perhaps make yourself a very cool, high-res 3D model of the earth.

It’s not clear how accurate the data is. The reports seem to say within 9m vertical accuracy. But I assume this is measuring the “surface” that the Shuttle saw – so that would include roof tops. But with smoothing/filtering, would this be washed out to represent an average ‘ground height’?

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Responses

  1. Leszek Pawlowicz says:

    June 12th, 2007 at 8:59 pm (#)

    My experience with creating sea level rise simulations:

    http://freegeotools.blogspot.com/2007/04/sea-level-rise-storm-surge-and-flooding.html

    http://freegeotools.blogspot.com/2007/05/high-resolution-sea-level-rise-flooding.html

    showed me that the building height data is not “washed out” in SRTM. Using SRTM data for a flooding simulation of Manhattan results in less flooding than using standard NED data that conforms to the ground, because the building heights skew the SRTM data. Those results are even more pronounced for a low flat area like South Florida; GTOPO30 data shows average land elevations of less than a meter in the Miami area, while SRTM30 data shows elevations of 4-8 meters.

  2. Jonathan Stott says:

    July 12th, 2007 at 6:58 pm (#)

    Hi, Thanks for the EarthTools.org mention! I notice that Leszek mentions that buildings skew the SRTM data – this is an obvious artifact of the data being acquired using radar from a space shuttle. A good example is in London: http://www.earthtools.org/map/51.50468231156/-0.013475418090820312/14/0/Contour/ – a small mountain exists (about 30m high) around Canary Wharf and the Dome on the other side of the river (near North Greenwich) is picked out nicely by the 10m contour line!

    Sadly no better free data exists for the UK. Better data does exist for America (and Canada), but it will take me a while to process it and integrate it with the SRTM data.

  3. Versicherungen vergleichen says:

    August 29th, 2008 at 7:45 pm (#)

    Thanks, you wrote wonderfull.