Map error - Castle Pk Tr Calif

Pete Sandrock's Avatar

Pete Sandrock

30 Jul, 2020 07:29 PM

The Castle Peak Trail (Calif) is blocked by vertical cliffs ~750' east of Castle Peak. See the red marker here: https://caltopo.com/m/1QSH.

The map shows a trail passing west to east below the south face of Castle Peak to a junction with the Warren Lake Trail. The map contours immediately east of Castle Peak depict an easy descent, not the cliffs that block the trail. Another hiker using All Trails found the same problem with her app. East of the cliffy area, we could see the trail continuing an easy descent along the ridge toward the Warren Lake Trail intersection.

The attached photo shows the south face of Castle Peak on the left. The trail passes just below the peak from left to right before crossing the ridge to top the series of cliffs on the right. The rock is loose and crumbly, not suitable for hiking or easy scrambling.

  1. Support Staff 1 Posted by Julie on 30 Jul, 2020 10:10 PM

    Julie's Avatar

    Hi Pete,

    Thanks for contacting us. MapBuilder Topo draws largely from Open Street Map (OSM) data. OSM is a crowdsourced compendium of mapping information. Users and participants can upload tracks to OSM and draw trails. As a map is a representation of what's on the ground, they are not always perfect. One person's idea of a trail or route does not always match another's, or terrain can change over time and the map will stay the same until someone re-visits that area and then goes to make that change in the underlying data.

    It's possible to edit the map itself at https://openstreetmap.org. Since we typically pull from OSM quarterly for updates, you would see any edits in the CalTopo layers within 3-4 months typically.

    Best,
    Julie

  2. Julie closed this discussion on 30 Jul, 2020 10:10 PM.

  3. Pete Sandrock re-opened this discussion on 30 Jul, 2020 11:07 PM

  4. 2 Posted by Pete Sandrock on 30 Jul, 2020 11:07 PM

    Pete Sandrock's Avatar

    Hello, Julie,

    What really baffles me is that the map countours don’t show a series of drop-offs. Instead they indicate a smooth, gentle descent along a ridge line. Whatever the reason, the cliffs don’t show up on the map.

     

    I could see how a user might trace a trail across the area based solely on map contours but never ground-truthed it. Then it showed up as a trail in Cal Topo and All Trails.

    Pete

  5. Support Staff 3 Posted by Julie on 31 Jul, 2020 12:14 AM

    Julie's Avatar

    Hi, Pete,

    It's quite common for contours to not capture many real-world fall hazards. It takes really advanced surveying, usually from LIDAR generated both from planes flying over and satellite processes to record such detailed elevation changes. Luckily, a lot of that data is available and we are always working on keeping up with the most detailed elevation data available in the world. Even then, the scale of measuring such things is not nearly the same as would be important to a human being navigating the space. Consider how much time and effort it takes for a road crew to survey before constructing a new highway, or when a surveyor comes to measure the property you live on. That level of exact measurement is just not feasible for all the wildlands of the world. So no, the maps aren't a perfect representation of the land, and they never will be or else they would no longer be a map.

    However, CalTopo provides the tools to quickly consult a lot of maps that cover the same area. Looking at Castle Peak, if you switch to the FS 2016 layer, you see there is not trail designated at that spot. This would be a good indication that it's not an official and maintained trail. You could also look at the 2013-2015 NAIP layer and see that there are some big objects and open, rocky ground there. Add a contour overlay and while it might not show every cliff, you can tell that it's quite steep around that area and could logically conclude that there might be hazards. We can't give you a perfect map, but we can give lots of the tools to evaluate the terrain.

    Best,
    Julie

  6. Julie closed this discussion on 31 Jul, 2020 12:14 AM.

  7. Pete Sandrock re-opened this discussion on 31 Jul, 2020 12:17 AM

  8. 4 Posted by Pete Sandrock on 31 Jul, 2020 12:17 AM

    Pete Sandrock's Avatar
    Very helpful insights. Thank you!

    From: [email blocked]
    Sent: July 30, 2020 17:14
    To: [email blocked]
    Reply-to: [email blocked]
    Subject: Re: Map error - Castle Pk Tr Calif [Bug Reports #5005]

    #ssc24769 pre{width: 92%;margin: 10px 2%;padding: 5px 2%;background: rgb(239, 239, 239);border: 1px solid rgb(214, 214, 214);}#ssc24769 blockquote{margin-left: 0;padding-left: 1em;border-left: 5px solid rgb(204, 204, 204);}

    // Please reply above this line
    ==================================================

    From: Julie (Support staff)

    Hi, Pete,

    It's quite common for contours to not capture many real-world fall hazards. It takes really advanced surveying, usually from LIDAR generated both from planes flying over and satellite processes to record such detailed elevation changes. Luckily, a lot of that data is available and we are always working on keeping up with the most detailed elevation data available in the world. Even then, the scale of measuring such things is not nearly the same as would be important to a human being navigating the space. Consider how much time and effort it takes for a road crew to survey before constructing a new highway, or when a surveyor comes to measure the property you live on. That level of exact measurement is just not feasible for all the wildlands of the world. So no, the maps aren't a perfect representation of the land, and they never will be or else they would no longer be a map.

    However, CalTopo provides the tools to quickly consult a lot of maps that cover the same area. Looking at Castle Peak, if you switch to the FS 2016 layer, you see there is not trail designated at that spot. This would be a good indication that it's not an official and maintained trail. You could also look at the 2013-2015 NAIP layer and see that there are some big objects and open, rocky ground there. Add a contour overlay and while it might not show every cliff, you can tell that it's quite steep around that area and could logically conclude that there might be hazards. We can't give you a perfect map, but we can give lots of the tools to evaluate the terrain.

    Best,
    Julie

    On Thu, Jul 30 at 04:07 PM PDT, Pete Sandrock wrote:

    Hello, Julie,

    What really baffles me is that the map countours don’t show a series of drop-offs. Instead they indicate a smooth, gentle descent along a ridge line. Whatever the reason, the cliffs don’t show up on the map.

     

    I could see how a user might trace a trail across the area based solely on map contours but never ground-truthed it. Then it showed up as a trail in Cal Topo and All Trails.

    Pete

    Having trouble reading this? View this discussion online: Map error - Castle Pk Tr Calif.

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  9. Support Staff 5 Posted by Julie on 31 Jul, 2020 12:20 AM

    Julie's Avatar

    Sure thing! We love talking about this stuff.

  10. Julie closed this discussion on 31 Jul, 2020 12:20 AM.

  11. Pete Sandrock re-opened this discussion on 31 Jul, 2020 12:28 AM

  12. 6 Posted by Pete Sandrock on 31 Jul, 2020 12:28 AM

    Pete Sandrock's Avatar
    I did detect a level of unexpected enthusiasm in your writing. 😉

    I looked at NAIP '13-'15 and see what you described. 
    From: [email blocked]
    Sent: July 30, 2020 17:20
    To: [email blocked]
    Reply-to: [email blocked]
    Subject: Re: Map error - Castle Pk Tr Calif [Bug Reports #5005]

    #ssc24772 pre{width: 92%;margin: 10px 2%;padding: 5px 2%;background: rgb(239, 239, 239);border: 1px solid rgb(214, 214, 214);}#ssc24772 blockquote{margin-left: 0;padding-left: 1em;border-left: 5px solid rgb(204, 204, 204);}

    // Please reply above this line
    ==================================================

    From: Julie (Support staff)

    Sure thing! We love talking about this stuff.

    On Thu, Jul 30 at 05:17 PM PDT, Pete Sandrock wrote:

    Very helpful insights. Thank you!

    From: [email blocked]
    Sent: July 30, 2020 17:14
    To: [email blocked]
    Reply-to: [email blocked]
    Subject: Re: Map error - Castle Pk Tr Calif [Bug Reports #5005]

    #ssc24769 pre{width: 92%;margin: 10px 2%;padding: 5px 2%;background: rgb(239, 239, 239);border: 1px solid rgb(214, 214, 214);}#ssc24769 blockquote{margin-left: 0;padding-left: 1em;border-left: 5px solid rgb(204, 204, 204);}

    // Please reply above this line
    ==================================================

    From: Julie (Support staff)

    Hi, Pete,

    It's quite common for contours to not capture many real-world fall hazards. It takes really advanced surveying, usually from LIDAR generated both from planes flying over and satellite processes to record such detailed elevation changes. Luckily, a lot of that data is available and we are always working on keeping up with the most detailed elevation data available in the world. Even then, the scale of measuring such things is not nearly the same as would be important to a human being navigating the space. Consider how much time and effort it takes for a road crew to survey before constructing a new highway, or when a surveyor comes to measure the property you live on. That level of exact measurement is just not feasible for all the wildlands of the world. So no, the maps aren't a perfect representation of the land, and they never will be or else they would no longer be a map.

    However, CalTopo provides the tools to quickly consult a lot of maps that cover the same area. Looking at Castle Peak, if you switch to the FS 2016 layer, you see there is not trail designated at that spot. This would be a good indication that it's not an official and maintained trail. You could also look at the 2013-2015 NAIP layer and see that there are some big objects and open, rocky ground there. Add a contour overlay and while it might not show every cliff, you can tell that it's quite steep around that area and could logically conclude that there might be hazards. We can't give you a perfect map, but we can give lots of the tools to evaluate the terrain.

    Best,
    Julie

    On Thu, Jul 30 at 04:07 PM PDT, Pete Sandrock wrote:

    Hello, Julie,

    What really baffles me is that the map countours don’t show a series of drop-offs. Instead they indicate a smooth, gentle descent along a ridge line. Whatever the reason, the cliffs don’t show up on the map.

     

    I could see how a user might trace a trail across the area based solely on map contours but never ground-truthed it. Then it showed up as a trail in Cal Topo and All Trails.

    Pete

    Having trouble reading this? View this discussion online: Map error - Castle Pk Tr Calif.

    Reply with #ignore to stop receiving notifications for this discussion.

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    Having trouble reading this? View this discussion online: Map error - Castle Pk Tr Calif.

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  13. Meghan closed this discussion on 31 Jul, 2020 02:04 PM.

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