GPS for Iphone?

[johngo]

Actually, I had another idea regarding accuracy.
USGS maps are generally very accurate for things like streams, contours, and landforms like summits and ridges.

However, depending on the date that was created, they may be inaccurate for things like trails, which hikers are more interested in. If the map was originally created and say 1970, here we are almost 45 years later using the same base map.
Any trails that have been created on that map since 1970 are likely not to appear.

For this reason, having multiple map layers available to you, especially on a GPS, can be very helpful.

In Gaia GPS, the map layer Open Cycle seems to have the most up-to-date trails information. This is what's called an open-source map, which means it's free, and the content is created by the users, so it's usually much more up-to-date regarding trail information.

Don't let the "cycle" part of the map name for you. It has loads of backcountry trails and wilderness areas where bicycles will never go.

So, if your question about accuracy relates to "Hey, I'm not seeing my trail on this USGS map?!" Pull up the open the cycle layer and have a look for there.

Both Caltopo and Gaia GPS have the map layer Open Cycle, it can be very helpful. Have a look and let me know what you think.

[Koda]

true, the trails in the USGS maps can be lacking newer trails. I'll update my last comment to say the USGS topography is most accurate, I wouldn't trust Open Cycle topography at all, but if your staying on trails it might be more current.

[woodswalker]

The place where I am finding them inaccurate is so far on Mt Hood. Not by much. Everywhere else is good. Even the Wallowas was great. But for example cooper spur trail will show that I am not on the trail. That I am in fact still on the Timberline eventually it curves around but will say I am actually a few hundred feet east of the trail. Similar in Eden Basin area.When I compared my track later it was identical to what a paper copy of a Geo graphics map showed but different than what caltopo was showing. Over all I have found Gaia to be awesome and super easy to use. I would recommend it highly.
Woodswalker

[miah66]

Alot (most) of the trails shown on maps were created before the advent of GPS, and maps were more for pictorial information than exact location. Example: The trail on the left goes here, climbs the ridge, etc. It didn't really matter if it excluded a minor switchback or whatever. Many (most) of my GPS tracks have sections where the alignment is way off the "mapped" trail, or shown several contours higher or lower than it "actually" is. After all, the people making those maps were working in offices possibly hundreds of miles from where the map was depicting. They are also human too, and make mistakes. I sometimes forget there wasn't a "google man" with a backpack trekking the actual trail and recording the information to be published later that day...but that would've been nice!

[woodswalker]

Alot (most) of the trails shown on maps were created before the advent of GPS, and maps were more for pictorial information than exact location. Example: The trail on the left goes here, climbs the ridge, etc. It didn't really matter if it excluded a minor switchback or whatever. Many (most) of my GPS tracks have sections where the alignment is way off the "mapped" trail, or shown several contours higher or lower than it "actually" is. After all, the people making those maps were working in offices possibly hundreds of miles from where the map was depicting. They are also human too, and make mistakes. I sometimes forget there wasn't a "google man" with a backpack trekking the actual trail and recording the information to be published later that day...but that would've been nice!

That makes sense to me. I remember years ago when I was still lurking I would see reports that gave a correction to map inaccuracies. I only find it disconcerting at trail junctions where there are a lot of user trails
Woodswalker

[aiwetir]

I update OSM almost every time I go on a hike and I've considered starting a thread here where people could send me their GPX files when they find inaccuracies. OSM topography is rudimentary but if I can get the trails correct, then there many routing options available from different sources. You can then overlay the 'correct' route over a more correct USGS topo and get the best of both worlds.

[kepPNW]

Yeah, Miah beat me to it. Those USGS/USFS trails are often best-guess garbage. (In fact, just read a TR an hour or so ago, where the hikers were misled by them and crossed a river at a less-than-optimal location due to <cough> "cartographic generalization.") I don't keep up with OSM, but use (and contribute to) NWTopos instead. User-sourced rocks.

[Koda]

one of the open source user contributed topographic maps Id like to see become more popular is Toposm.com, it uses Open Street map as a base....

http://toposm.ahlzen.com/

the topography looks very detailed and accurate and the map is well done. Problem is it doesn’t seem to be used anywhere and doesn’t even have trails shown. I find it odd that Open Street is developing their Open Cycle map more than this for outdoor use... you would think they would easily layer the OC Map trails over the toposm map...

[woodswalker]

Great sources and info. Now that I have been using GPS for about a year it all is starting to make sense in terms of available resources that are out there.

[aiwetir]

Yeah, Miah beat me to it. Those USGS/USFS trails are often best-guess garbage. (In fact, just read a TR an hour or so ago, where the hikers were misled by them and crossed a river at a less-than-optimal location due to <cough> "cartographic generalization.") I don't keep up with OSM, but use (and contribute to) NWTopos instead. User-sourced rocks.

I'd do NWTopos, but I once spent a few weeks adding hundreds of miles of logging roads to OSM while I was laid up with a broken back. I'm in too deep. Although since OSM gets used by so many services that route with it, I suppose I could easily generate a gpx to send to NWTopos with 2 clicks. It would be the same exact trail too.

one of the open source user contributed topographic maps Id like to see become more popular is Toposm.com, it uses Open Street map as a base....

http://toposm.ahlzen.com/

the topography looks very detailed and accurate and the map is well done. Problem is it doesn’t seem to be used anywhere and doesn’t even have trails shown. I find it odd that Open Street is developing their Open Cycle map more than this for outdoor use... you would think they would easily layer the OC Map trails over the toposm map...

That looks very interesting. I don't see any OSM stuff I've added since 2011 though, and the github page shows the last updates were 3 and 4 years ago. I suppose since it's open source, someone could update the whole mapset with trails too