Map Accuracy On Gpsmap60c

[+TeamBix]

The installed base map on my 60C is way off - marking a waypoint at a local park shows up on the map as in the middle of a river (which in reality is about a half mile away). Does installing CitySelect improve accuracy - or will it still mark in the river???

[CenTexDodger]

Just so we are clear, city select will not improve the accuracy of the GPS, but it is a more accurate representation of where man-made things are such as streets, roads, businesses and such. As Far as rivers are concerned, US Topo is a more accurate representation of where rivers run and such.

[+njload]

Is the waypoint one you created? If not you have to take into consideration the accuracy of the GPS that placed it. When I'm GeoCaching I consider anything within 20 feet a good find.

 

Just my 2 cents worth.

 

NJLOAD

[+Night Stalker]

I see a great increase in accuracy of the City Select maps in my area except on my street. For some reason it is about 100' off to the East of the actual location. It is interesting to note that the Topo Maps on my Magellan were off the same distance in the same direction. I have to assume that both companies use the same source for their maps.

[+TeamBix]

Several waypoints were downloaded to my GPSMAP60C from geocaching.com. The accuracy between what I downloaded and actual locations were right on the money. It's just that the basemap installed with the unit shows a string of waypoints out in the middle of the river...and when I am standing at one of the waypoints, the basemap shows me standing about 100 yards out in the river.

 

So...accuracy of the unit itself is not in question....the waypoints and the GPS match up.......it's the graphical representation of the basemap. That's why I was asking if it improves if I purchase and install something like CitySelect. That way it doesn't show me walking on water when I'm actually on dry land.

[stevesisti]

Several waypoints were downloaded to my GPSMAP60C from geocaching.com. The accuracy between what I downloaded and actual locations were right on the money. It's just that the basemap installed with the unit shows a string of waypoints out in the middle of the river...and when I am standing at one of the waypoints, the basemap shows me standing about 100 yards out in the river.

 

So...accuracy of the unit itself is not in question....the waypoints and the GPS match up.......it's the graphical representation of the basemap. That's why I was asking if it improves if I purchase and install something like CitySelect. That way it doesn't show me walking on water when I'm actually on dry land.

There are 2 factors, the "accuracy" of the map, and the "resolution" of the map. In a simple example, if the state of Florida was displayed using 3 points (less memory, as in a base map) the "rounded" shape of the tip on Florida would have to become a "point". Any major bay or cove along either coast side would be eliminated because you only used three points. The more points you use to define the coast line, the more "resolution" you have.

 

City Select uses many more "points" to define land shapes than the base map, hence it is more "accurate" as far as displaying your position on the map screen. To carry this even further, I have made maps duplicating the 1:24 K topo maps, using as many points as I decide is necessary to define an "accurate" shoreline for example. With the homemade map, I never see my position as "out in the water" when in fact I am on "dry land" It is much more "accurate" than either City Select or Topo at displaying position on the map. The downside is that since I'm using more points to more accurately define these contours, my "Homebrew" maps use more memory. There is obviously a trade-off between map resolution and map size (memory wise), which in fairness, given the memory limitations of some of the handhelds, Garmin seems to have struck a good balance.

 

Using the "zoom" at a reasonable level you will find the City Select or topo much more "accurate" than the base map alone....If I'm not mistaken the 60CS has an 8MB base map for the whole country.....in city select the state of New York is more than 54 MB... you can see how many more points you can use to define shapes with the larger file sizes for a given area.

 

Steve

[BilgeRat]

I use a 60c and City Select to find waypointed boat ramps along the Lower Mississippi, and I find that many (not all, however) of the levee roads are actually represented. You can also record tracks of roads that are not on the map and send them to Garmin, and they will incorporate the tracks into new versions of the software. The basemap won't do that!

Tom

[+webscouter.]

The short answer to your question is yes. Rivers and lakes are more accurately represented on City Select as are roads.

 

Garmin maps are provide by Navtec. If you find an error in one of the maps you can submit it at http://www.navteq.com/updates/mapfeedback.html

[+alanfreed]

Keep in mind that the basemaps aren't really meant to be super, super accurate. They're really just a rough map for the sake of having *something* preloaded into the unit. Bear in mind that you're getting the entire country (and much of the rest of the world) crammed into that unit.

 

The best way to use any of the mapping receivers is to buy the software. You will indeed find instances where the basemaps appear to be off the mark, and you'll notice that highways have rigid lines rather than the smooth curves offered by the better software.

[+graveldick]

Hi all.

 

I too noticed this mapping inaccuracy in the base map on my 60cs. I asked the Garmin dealer here in Western Australia what the cause was. I was told that the base maps are designed as a guide only.

[+silverquill]

Keep in mind that the basemaps aren't really meant to be super, super accurate. They're really just a rough map for the sake of having *something* preloaded into the unit. Bear in mind that you're getting the entire country (and much of the rest of the world) crammed into that unit.

That is reassuring (sort of) because last night my Magellan showed me driving right into a lake! Nice trick, but, alas, I was still on dry land. Unfortunately, I can't get my Topo 3D to run on my computer and Magellan support has been abysmal.