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Cool service, albeit it's for smaller uses. The limit is 25,000 requests a day. This sounds like alot, until you realize each point is a request. So, you wan

Cool service, albeit it's for smaller uses. The limit is 25,000 requests a day. This sounds like alot, until you realize each point is a request. So, you want elevations for a 100 mile route drawn on a map? That's about 2-3000 points, so you only get 10-20 of such routes before hitting your daily limit. Other issue is the accuracy: I am not sure the base DEM resolution they are using, but my guess is it's the standard 10meter spacing between points inside US and territories, and 30meters outside. 10meter grid spacing isn't bad at all, it's actually pretty good, but their algorithm for interpolating is non-existent. For any point not directly on a grid point, they just average the four surrounding elevations and return that. I have played with several interpolation schemes, and I have found either a bilinear or a cubic interpolation for interior points to be vastly superior to a nearest neighbor or averaging scheme. Differences can be easily up to 10 meters for a 10meter grid spacing. I had been hoping they'd release this, but I'll stick to my home-brewed service with the 500gig NED at 10 meter resolution (1/3 arcsecond). No API limits :)

Tichy 17y ago
Might also be useful for augmented reality apps, to the elevation of virtual objects right.
dougmccune 17y ago
[Edit: as pointed out below it seems like it really is 25,000 unique locations, my mistake.] so you only get 10-20 of such routes before hitting your daily limit. Not true, from the usage docs: Up to 1,024 locations may be queried within a single request. So that's really a theoretical max of 25,600,000 locations per day if you maxed out every request.
- borism 17y ago
  Not true, from the usage docs: Up to 1,024 locations may be queried within a single request. "Note that on any given query, you may request elevation data for multiple locations, which count as separate queries." Approximate! No need to do a lot of requests for flat land!
  - cullenking 17y ago
    Approximations only get you so far. Try telling picky cyclists, who compare your calculated elevation gain/loss to ten other sources out there, that you just want to approximate :)

Tichy 17y ago

Might also be useful for augmented reality apps, to the elevation of virtual objects right.

dougmccune 17y ago

[Edit: as pointed out below it seems like it really is 25,000 unique locations, my mistake.] so you only get 10-20 of such routes before hitting your daily limit. Not true, from the usage docs: Up to 1,024 locations may be queried within a single request. So that's really a theoretical max of 25,600,000 locations per day if you maxed out every request.

borism 17y ago
Not true, from the usage docs: Up to 1,024 locations may be queried within a single request. "Note that on any given query, you may request elevation data for multiple locations, which count as separate queries." Approximate! No need to do a lot of requests for flat land!
- cullenking 17y ago
  Approximations only get you so far. Try telling picky cyclists, who compare your calculated elevation gain/loss to ten other sources out there, that you just want to approximate :)