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Is The Geocache Elevation on the Cache Page?


Inmountains
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Maybe I am just getting blind in my old age, but I can't seem to find the geocache elevation on the cache page. I added the Elevation column to GSAK but when I bring in the file, they all state a 0.0F elevation. When I do a Project GC, it shows my the ten highest and the ten lowest elevations, but I do not see where Project GC gets the elevation. Can someone point me in the right direction?

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On the website I havn't found anything, but there maybe a workaround:

 

On the "Geocache Google Earth Viewer" tab click on "Download Viewer" which will open Google Earth with all the available cache. Navigate to the cache in question and place the cursor right on it. On the bottom of Google earth you can see the elevation of this location.

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No.

 

Right, and that's how it should be. In many cases it's meaningless, and in some it's a potential spoiler (eg, steep terrain changes at GZ). In the case of wilderness caches where it is potentially useful, the cacher probably already has topo maps stored in the gpsr.

It can be helpful as well.

 

I did an earthcache yesterday that required noting elevation.

 

Our car GPS (Nuvi 2595LMT) and Oregon 600 showed elevation numbers that were about 5 meters off from each other.

The elevation value in GSAK told me which device was reporting the more accurate value.

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Why do you trust GSAK's elevation more than GPS elevation?

It's not so much trusting it over the GPS, it's using that info in GSAK to figure which GPS is reporting the more accurate value.

 

I don't have topo maps for my Oregon, so it's all I have access.

 

The Oregon 600 was reporting 97 meters at the posted (top of the drumlin) while the Nuvi was reporting 105 meters.

GSAK indicated that the posted was at 97 meters.

 

Do you know its provenance?

GSAK gets it's elevation data from Mapquest, USGS, SRTM, Google, and Aster (in that order).

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On caches in the US, there are mapping links on each cache page - some of which offer a topo map, cache as marker on map:

MyTopo Maps - always

OpenCycle (sometimes)

OpenStreetMap (sometimes)

MSR Maps (Formerly Terraserver) used to but now appears to be broken, redirects to MS search???

 

 

Here's the complete list of mapping for caches from each US cache page:


  •  
  • Geocaching.com Map - NO TOPO
  • MyTopo Maps
  • Google Maps - NO TOPO
  • MapQuest - NO TOPO
  • Bing Maps - NO TOPO
  • MSR Maps (Formerly Terraserver)
  • OpenCycleMap
  • OpenStreetMap

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On caches in the US, there are mapping links on each cache page - some of which offer a topo map, cache as marker on map:

MyTopo Maps - always

OpenCycle (sometimes)

OpenStreetMap (sometimes)

MSR Maps (Formerly Terraserver) used to but now appears to be broken, redirects to MS search???

 

 

Here's the complete list of mapping for caches from each US cache page:


  •  
  • Geocaching.com Map - NO TOPO
  • MyTopo Maps
  • Google Maps - NO TOPO
  • MapQuest - NO TOPO
  • Bing Maps - NO TOPO
  • MSR Maps (Formerly Terraserver)
  • OpenCycleMap
  • OpenStreetMap

Here in Australia there's no MyTopo option, but the OpenCycleMap shows topographic contours. Unfortunately they bear little resemblance to what the ground actually looks like. For example, here's what I see on that map for the nearby Mount Ettalong headland:

headland1.png

From that, it'd be easy to imagine a gently sloping hill you could easily walk down from the top at a bit over 60 metres to the sea, but the reality is quite different. Here's what a real topographic map shows:

headland2.png

The actual headland is a sheer cliff dropping from a plateau down to the rocks along the water's edge.

Edited by barefootjeff
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Maybe I am just getting blind in my old age, but I can't seem to find the geocache elevation on the cache page. I added the Elevation column to GSAK but when I bring in the file, they all state a 0.0F elevation. When I do a Project GC, it shows my the ten highest and the ten lowest elevations, but I do not see where Project GC gets the elevation. Can someone point me in the right direction?

 

Here is Project-GC's FAQ article about how they calculate elevation data...

http://project-gc.com/Home/FAQ#4179902386

 

How is the elevation data calculated?

 

This is actually quite advanced, but we will try to simplify it a bit.

 

First off, we use different data sets for different areas on the earth. For most of the planet we are using data from the SRTM1 and SRTM3 databases created by Nasa. Nasa has created this data by measuring the height using satellites. SRTM1 has a higher resolution, but that data only exists around USA. SRTM3 exists for other parts of the world, except closer to the poles.

 

The SRTM1 data has ONE measure point per 30x30 meters, and the SRTM3 data has ONE measure point per 90x90 meters. What this means, is that there is no measurement for every coordinate, and therefore not for every geocache location. So what we do is that we interpolate between the 4 closests values to get a weighted average for the geocache location. In an area which is very hilly, like mountains, this will give a quite big fail factor and almost always a too low value. There is however no better way to do this, since the measurements just doesn't exist, well, except manually adding data for all the geocaches, which we do not do.

 

Other services like for example Geonames might have slightly different approaches to how they calculate the data, therefore we will have smaller differences. But they do have similar solutions.

 

Before using SRTM as our primary source we used AsterGDEM which is created by radar measurements. This data has measure points for every 30x30 meters in a larger area of the earth, which in one way makes it better. But, AsterGDEM is also known for being affected by radar shadows, which makes the data quite useless for some areas. We have found out that switching to SRTM has giving us more precise data.

 

For those areas where there is no SRTM1 or SRTM3 data we are falling back to other services which relies on other data.

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There was an an greasemonkey add-on that put the elevation on the page after the cache name, but can't find anything about it now

 

I wrote a Greasemonkey script a few years back which adds the height in metres to a cache listing, next to the coordinates. You can get it from https://openuserjs.o...Geocache_Height - there's also a version which works in feet. The height data comes from Google, and has the usual caveats about taking its accuracy with a pinch of salt.

 

screenshot.png

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The SRTM data is nice enough for unpopulated areas, but the 30x30m resolution is not that great, especially near sudden topographical anomalies (e.g. cliffs, peaks).

 

For my own stuff, in the USA, I use the USGS NED dataset, which has a horizontal resolution of 30 meters at worst, and 3 meters at best. It performs better than the GSAK script I have used, IMO.

 

If that fails, I fall back to Google, which can be used for limited queries. It uses a DEM that is usually equivalent to the 3m USGS.

 

I only fall back to STRM datasets if everything else fails.

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There was an an greasemonkey add-on that put the elevation on the page after the cache name, but can't find anything about it now

 

I wrote a Greasemonkey script a few years back which adds the height in metres to a cache listing, next to the coordinates. You can get it from https://openuserjs.o...Geocache_Height - there's also a version which works in feet. The height data comes from Google, and has the usual caveats about taking its accuracy with a pinch of salt.

 

screenshot.png

 

Yup thanks that's the one

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I don't trust the elevations that Project GC is pulling in necessarily anyway.  According to them, my lowest elevation is GC2BG62, at -10 feet.  This is near a river in Rhode Island.  Since the river is flowing into the ocean (about 1 mile away), rather than the ocean flowing into the river valley, I'm not sure how it could even pick up anything at a below-sea-level altitude there.  A couple other finds of mine further upstream are also listed as being below sea level.

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4 hours ago, rosebud55112 said:

I don't trust the elevations that Project GC is pulling in necessarily anyway.  According to them, my lowest elevation is GC2BG62, at -10 feet.  This is near a river in Rhode Island.  Since the river is flowing into the ocean (about 1 mile away), rather than the ocean flowing into the river valley, I'm not sure how it could even pick up anything at a below-sea-level altitude there.  A couple other finds of mine further upstream are also listed as being below sea level.

Find a cache at the dead sea. ;)

Edit: Elevation data usually comes with a possible error of 90 meters, or 30 in the best case.

Edited by Rebore
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