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Very new, do I want a gps?Waypoints in woods only.

capefifer 0 Points
edited November -1 in GPS Discussions
Looking for a little quick info which I can't get from the teenager at Canadian Tire.I am thinking of replacing my map and compass with a gps. I don't want it for road maps,driving or geocaching.I can get a Garmin etrex 20 for around $200. I like the look of the display,the price is okay and reviews seem positive.I am wondering how detailed the map would be for my area(scale and rivers,etc.)and how much this map would cost me.I understand it comes with some type of map loaded or that I can load,but really have no idea. I want this for as I said replacement of maps and compass when i am in the woods. I would like to be able to set waypoints when I come across something of interest and enter brief notes pertaining to whatever it is(farm house etc.)I would need no future upgrades as the lay of the land shouldn't change in my lifetime.I would like to be able to download information to a map on computer also if that is possible?Really, wondering about connecting with computer and how large a map I get for what price then how detailed I can scale map down to. My area of travel is really no larger than~50mi. by 50mi. and I would like to be able to scale down to ~200'/inch or better.Can i do this with one map download or how much would it cost me?Also, can the gps hold more than one map? Really don't have a clue,help,tired of folding maps. Thanks

Comments

  • sussamb 798 Points
    The Etrex 20 will certainly do what you want and yes, you can load more than one map, I have 3 on mine.

    The basemap that it comes with though is pretty much useless for the sort of use you're talking about, but there are many free maps for Garmin handhelds out there but it depends which area of the world you want them for.

    There is extensive map coverage in the UK, and in many parts of the US and Canada, and loaded maps can be viewed on your PC using Garmin's Basecamp program. Have a look here for some more info:

    http://wiki.openstreetmap.org/wiki/WikiProject_Canada
  • Boyd 1974 Points
    The standard for detailed topographic maps is 1:24,000 scale, which means that items on the map are 1/24,000 of their actual size. These are commonly known as "24k maps".

    Using your example, you want 200 feet to equal one inch and 200 x 12 = 2,400 so you are asking for a 1:2,400 map. That is WAY beyond the precision of any mapping you will find anywhere. It would be 100x the resolution of a 24k map!

    However, you can subscribe to Garmin's Birdseye download service ($30 USD for unlimited downloads) and you will get close to this kind of precision in aerial photographs. Each pixel on your screen represents about 2 feet in the real world. Doing a little more math, the eTrex 20 screen is 1.4" wide and has 176 pixels. So 176/1.4 = ~126 pixels per inch. At 2 ft/pixel resolution that would mean one inch on the screen would represent 252 feet in the real world.

    So really, I'm afraid your expectations for accuracy are unreasonable on a consumer level device with consumer grade mapping. With the eTrex you could also make your own maps, if you could find higher resolution aerial imagery. For example, 1 foot per pixel imagery is available in many areas of the US, and sometimes you will find even higher resolution in urban areas. No idea what's available in Canada. But due to the limits of Garmin's "custom map" format, if you make your own map from 1 foot per pixel imagery it is only possible to cover an area of about 2 miles x 2 miles.

    For an example of what's possible, have a look at the screenshots of this map I made of downtown Philadelphia with very high resolution data:

    http://www.gpsfiledepot.com/maps/view/237/

    But realize that these screenshots came from an Oregon which has a bigger screen with 2.5x the number of pixels as your eTrex. So you would see less than half of what you see on the Oregon screen for a given zoom level.

    Now, if you want to see what kind of Garmin topo maps are available, this is their Topo Canada product:

    https://buy.garmin.com/shop/shop.do?cID=255&pID=1016

    But these are 50k maps - 1:50,000 scale - which is pretty low resolution. If they existed, the 1:2400 scale maps that you claim to desire would be about 400x more accurate than a 1:50,000 scale map. Nevertheless, you can view these maps here:

    http://www8.garmin.com/cgi-bin/mapgen/webmap.cgi?p=25493505&u=1&v=0&cp=78C9585AEF53D85A&z=2&w=600&h=450&d=0&rz=0&k=1&sc=1

    You might also browse the free maps for Canada at GPSFileDepot. Of course, none of them will come anywhere near the level of detail you want either.

    http://www.gpsfiledepot.com/maps/country/ca
  • sussamb 798 Points
    Boyd, just wondering if the OP meant the scale the way you've interpreted it? I interpreted it a different way and that was that the OP wants to be able to zoom in on his Etrex to about an inch equalling 200 feet? If he did then at maximum zoom an inch equals around 12 metres.

    Course the map's a bit blurred at that point :lol:
  • Boyd 1974 Points
    You could be right, don't know. But you are way beyond the accuracy limits of any consumer device at that point, which is about +/- 16 feet. You are also beyond the limits of Garmin's map format which can only represent objects with +/- 8 foot accuracy.

    To me, this implies that he's going to be disappointed with any consumer grade device. Let's say we have a stake in the ground at a known location and you visit it and create waypoint "A" on the first day. Now you return a second day and record waypoint "B". Each of those waypoints should be within 16 feet of the actual location if the GPS is performing up to specs.

    However, "A" might be 16' North of the correct location and "B" might be 16' South of it. So the GPS could be performing within specs and you could record two waypoints at the same spot yet they would be 32 feet apart on the map.
  • sussamb 798 Points
    I sure follow all that ... :)

    He's talking though about saving waypoints etc so I'm guessing at some point he wants to be able to navigate back to them. I know when I'm trying to locate geocaches I zoom way in ... sure the map is blurred but I'm after the relative position between me and the cache. Actually at that point the map's irrelevant ... :wink:
  • Thanks to both of you,you were quite helpful.
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