snowfleurys

Five or six years ago I found two sources list 10-12? factors affecting gps accuracy. Today I found this on the Trimble web site http://www.trimble.com/gps_tutorial/howgps-error2.aspx Summary of GPS Error Sources Typical Error in Meters (per satellites) Standard GPS, Differential GPS Satellite Clocks 1.5, 0 Orbit Errors 2.5, 0 Ionosphere 5.0, 0.4 Troposphere 0.5, 0.2 Receiver Noise 0.3, 0.3 Multipath 0.6, 0.6

It would be helpful if you said which map as the numerous maps there are created by many different map authors.

Many consider the best GB maps are from http://talkytoaster.co.uk/ukmaps.htm

My OR300 takes about 10 seconds per Gb. The Canada topo by Ibycus is nearly 4GB.

Unless something has recently changed, the batteries can not be recharged while in the unit. This is to avoid the possibility of accidentally trying to recharge non-rechargeable batteries which could damage the batteries and possibly GPSr unit.

No. It is 39 full degrees and .55139 part of a degree. FYI - degress and seconds would be unworkable; a valid format would be degrees, minutes, and seconds.

As has been mentioned before, there is a cone of random location error in every reading. When you stop, the GPSr has no way of knowing if the next location obtained is due only to random error or if you actually changed position and it is supposed to re-orient the map using the previous location and the current location. People have learned to live/use paper maps with north always up. Why not set the GPSr to north up, then rotate the GPSr as you change directions while walking with the direction you are moving pointed ahead, and when stoped do not rotate the GPSr. Bug? ? IMHO there are way to many in Garmin's GPSrs, howevder, in this case I would say it is simply not using the GPSr as it was designed. Have you notified Garmin of this issue? May get fixed if you (and others) do, probably will not if you do not.

If it is important to have a crumb at the point of each switchback, you need to occupy that point for at least the minimum interval time you have the GPSr set to (and if you stay there too long, there will be multiple crumbs within a cone of position error). That is just the nature of how GPS/GPSrs opperate.

This has nothing to do with having a map displayed or even on the GPSr? The user's manual for your GPSr may have answers to some of your questions and some other interesting and useful info.

'I'd be looking a bit more closely. When comparing the 0.8 mile images, the TopoUSA version appears much cleaner, at least to my eyes.' Of course it does; TopoUSA is a 100k scale product displayed at/near its maximum data content; with the 24k topo you are forcing the full 24k detail (which is designed to be displayed at around the 800 ft zoom display) to be displayed at 0.8 miles by having the GPSr set to maximum detail. Looks like TopoUSA has a 10 meter contour interval in that area, while the KS? topo is using 20ft - that is over 1-1/2 times more contour lines being displayed. Set the display detail to normal, the way the mapsets were intended to be view, and make the comparisons. 'Notice below how the County names are drawn over the river and obscuring the river?' How and where names are displayed is determined in the Garmin GPSr. AFAIK, no 3rd party map author has determined how Garmin determines name display position nor how to modify it. And even if it was known, how practical would it be to individually tweek the position of millions of names per mapset? Plus which name gets displayed and where varries with display zoom level. Try turning display labels to off. 'See how the gpsfiledepot map doesn't color in the lake, but does for the coves?' There are thousands of coding errors in the source data which is publically available for third party authors to use. Notice how few people have come foreward to author a state topo mapset; even once, let alone upkeep and improve their initial creation. Look at the transportation. The 3 'top levels' used in the source files from Census are: interstate, highway, and residential. Besides the mis-codings; for their purposes of head and house counts any roadway with a house is considered residential irregardless of its highway status (local, county, state, or national).

JBnW - Explain '... they don't look as "clean". This might be because some users what more features and including them can make portions of a map 'cluttered'. It is also inappropriate to display most mapsets with 'Most Detail'. Do so is like taking a printed 24k topo and reducing it to 100k and not reducing the number of contour lines nor the number of features of feature types. It may work OK in areas where little info is available and/or where a feature type of interest is wanted to display at a more general zoom display level.

You should see the full detail of the PA topo at around the 800ft display zoom level with the display detail set to normal. Within the limits of available source data, it has as much detail as is on the printed USGS 24k topo maps. Does it have as much detail as the screen shots on gpsfiledepot? If not, you may be another victum of the profile issue. Some profiles do not display all the feature types in a mapset. Is not the PA topo displaying more detail than the Garmin base map? Did you try displaying the mapsets with only one enabled? Exactly what does 'more detail' mean to you?

The newer units use a different folder/file structure for tracks, route, waypoints which BaseCamp creates/recognizes, but MapSource does not. I think saveing the MS route to the computer, opening it in BC, and it can then be sent to the GPSr. 'How many people find ...' - Probably somewhat less than all who do not use it for Birdseye imagery. 'What was Garmin thinking?' - They created it to display and sell Birdseye imagery. 'Not everyone is a computer geek ...' - Garmin's staff needs improvement here as MS could have been modified to handle Birdseye or all the functionality of MapSource could have been included in BC. Just another example of wanting to get as much of the consumer's money as possible for as little cost to the manufacturer, etc. as possible.

With both maps enable you should be seeing the Garmin base map when zoomed-out and the topo maps when zoomed-in. There are various topo maps by various map authors creating their mapsets to address various purposes. Being specific on which topo mapset would help. Disable the Garmin mapset and you will see what the topo map displays at various zoom display levels. The topo mapsets will display from the 20' zoom display level out to a certain level (depends on what the map author has it set to), then if the Garmin base map is enabled, it will display from that level out to the maximum 'world' level. They usually will not display at the same time; however, there are some overlay/transparent mapsets which are intended and will display at the same time as a base map (topo or other). Depends on how you define better and what 'features' are important to you. The format for Garmin's 3D views has not been reverse engineered. Only Garmin has people type POIs (eat places, etc.) - that data is simply not publically available for map authors to include in their mapsets. Desert Southwest is routable, other topo mapsets downloadable from GPSfiledepot are not; nor do any? have address searching. You can view areas of you choice for Garmin's CityNavigator and 24k topo on Garmin's website.

USGS has recently stated that the DRGs (images of the topo printed topomaps) total about 238Gb and the DOQs (air-photo imagery) is nearly 17Tb (17,000Gb). How much you can get on the GPSr depends on the size of the micro memory card. How much area you have available depends on how much time you care to use downloading the imagery and how much computer storage space you have (or care to use). Use JbnW's info of 35-100Mb per 10x10 mile area. I would expect the more data on the GPSr, the slower it will perform.

Garmin's website allows you to view an area(s) of you choice for CityNavigator and 24k topo (and perhaps some of their other mapsets). Garmin products also include features which have not been reverse engineered.

Yes; kind of. For most USA printed maps the accuracy standard is that not more than 90% of the tested points will be within 1/50 of an inch on the published map. For a 1:24,000 scale map (1 inch on the map represents 2,000 feet on the ground) that is 40 feet. The accuracy standard(s) can vary by map scale, time and country. For most mapsets created for Garmin GPSrs the situation is more complicated. Coordinates are defined as 360 degrees divided by 2 raised to the 24 power (maximum). We call this the bit-level. Most mapsets will use three bit levels (some may use 2 or 4 depending on the type of data and what the map author is trying to show). Usually these are 23, 21, and 19 (OSM uses? 24, 22 & 20, likely because of all the building outlines available and the closer spaced street grid in the older cities). Either by default or by choice of the map author, the different features are defined to display to different zoomed-out bit-levels (it would over clutter a map display to show small buildings, ponds, intermittent streams, etc when displaying a large area on the GPSr). In each .img file in the mapset are three (+-) sets of map data; one each for the features and coordinates valid at each bit-level. The build software adjusts the more detailed coordinates and eliminates duplicate coordinate pairs and features too small to be shown as more than a point as it builds the more generalized maps. As far as I can tell, a 1:24,000 scale map would be between the 23 and 22 bit-level. On the GPSr this is about the 500 or 800 foot diplay level. There appears to be a small difference depending on which model GPSr the mapset is being displayed at. The GPSr and MapSource and BaseCamp will also allow you to change the amount of detail displayed; however, this affects all feature types and zoom-levels. Issues are created when users keep zooming-in beyond the most detailed scale of the mapset; there is no more data available, nor any more detail in the data or the locations; only empty magnification - the features are simply seperated/enlarged at the same rate. Think of enlarging a paper map on a copy machine. As far as Garmin's included basemap (probably 1:1,000,000 or 1:2,000,000); it's use would be when panning some distance and then zooming-in to the more detailed data. As far as your previous concern about accuracy; road next to steeply sloping glacier shapped valley side, moving bus (metal roof and sides) and unknown scale and production method of mapset on GPSr, I do not think 1,000 off is unreasonable, perhaps not even 500 ro 600 meters. Did you note the 'circle of error' on the GPSr and the configuration of the satellites? With most of the NE 1/2 half of the sky blocked by the valley side and likewise some of the SW, the pattern was more linear the triangular.

What I have found is that there is a 4Gb limit to the total size of selected quads/segments that MapSource or BaseCamp will put into a gmapsupp.img file. Each gives an error message if the total is larger. I selected 1/2 of an 8Gb mapset, sent it to the micro memory card, renamed the gmapsupp.img file to xxx_west.img; then did the same for the other 1/2, renaming it xxx_east.img. My OR300 shows it a a single mapset. At 80 seconds startup time when the card is in the OR300, I do consider it very useful. I have not tested to see if this is 10 seconds per Gb, nor if something could be changed to shorten the startup time.

What coordinates would be entered into the GPSr?

What do you intend to use it for?

the 'g' in Garmin needs to be 'G'.

MapInstall is used to load vector map data 'in' Bascamp. I have not found a way to start it from BaseCamp; but have not looked much as I prefer MapSource.

I think it is more a visibility issue of a larger screen size. 78 = 2.6 inch diagonal e30 = 2.2 "

I would guess it uses a very small term algorithm to calculate it from the long & lat.

Neither do those who are trying to assist you. If your display is not close to the screen shot on the mapset's webpage there may be an issue with the GPSr's settings. As you feel we are not allowed to ask for further information, nor expect what you say is accurate, I can not see why anyone should spend further time on this. Enjoy the Garmin mapset.