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How Much Internal Ram Is Really Needed?

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There are GPS out there that range from 0 internal RAM up to 115MB of internal RAM (GPSMAP76CS).


How much is actually gets used? Does more RAM = more maps you can hold at once?

or more detail and/or size on a single map only?


The amount of RAM seems unrelated to the number of route/waypoints a unit can store..bottom-end etrex with 0 RAM can store the same # of WPs as a Vista C with 24MB RAM, but can only store 1 route, while the Vista C can store 50..so RAM = more routes? Ah! However, the GPSMAP76CS with 115MB RAM only stores 2x as many WPs, and the same amount of route as the Vista C despite having almost 5x as much RAM..so what's the deal?


(side note: What is the difference between the listing of '# of WPs' and '# of Routes/# of WPs per route"?)


Are there any sites where I can do a side-by-side comparison of units from different manufactuers?

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The memory sizes listed for GPS receivers is *only* the memory available for maps. There is additional memory in the units for the firmware, for waypoints, routes, and for tracklogs, but AFAIK, that memory is not listed by any of the manufacturers.


The maps come in two basic forms: the basemap included with the unit, and the detailed downloadable maps. Garmin only ever advertises the space for the downloadable maps. For example, the VistaC actually has two memory devices inside. One is for the firmware and for the routes/tracklogs/waypoints/etc. and the second is a 32 MB chip for the basemap (8 MB) and the downloadable maps (24 MB). But Garmin only specifies the 24 MB that's to be used for the downloadable maps. Similarly, the 76cs has a 128 MB for maps of which 13 MB is used for the basemap while 115 MB is available for downloadable maps. OTOH, Magellan does generally explicitly list the size of their basemaps (i.e. 8 MB in the 330, 16 MB in the Meridian Gold, 2 Mb in the base Meridian, etc.).


Since the memory sizes only refer to the map memory, there is no real relationship between the memory size listed and the number of waypoints or routes/trackpoints that can be supported.


The more map memory a unit has, the larger the geographic area that can be covered with the detailed maps.


On your side note:

The number of waypoints is the total number that the unit can store. A route is basically just an ordered list of waypoints where you're going to go from the first waypoint to the second to the third, etc. and finally to the destination waypoint. So a unit can store a certain number of waypoints and can also have some number of lists (or routes) that each contain some of the waypoints.

Edited by peter
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if you have a magellan, you'll have to buy an SD card reader/writer in order to write multiple map sections to the same card. No big though - they're less than $10, and make the uploading process tons faster.


as far as what I can fit on a card:

(these are all from magellan MapSend directroute)


Southern California from Monterrey/Carmel to San Diego, including Los Angeles, and parts on Nevada, Utah, and Arizona: 39.5 mb




Buffalo, NY to Baltimore, MD -- including Buffalo, NY; Baltimore, MD; Harrisburg, PA; and part of suburban Washington DC: 37 mb




downtown Baltimore (only contains downtown area): 944 kb


New York city : 7.6 mb




Buffalo, NY; Rochester, NY; Allegheny, PA: 7.8 mb


Buffalo, NY; Toronto, ON; Barrie, ON; Hamilton, ON; MIdland, ON: 14 mb

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It definitely depends on the maps you need or want.


I have much of the densely-populated portion of San Diego county, plus many of the maps north a few hundred miles towards Death Valley National Park and Bishop, CA, and I'm only using 17% of the 24 MB available to me on my Garmin eTrex Vista. B)

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Go for more RAM!! You can never have enough! Seriously, my Etrex Legend (8Mb) is fine for waypoints. I then got the Europe (UK) mapsource and realised 8Mb is seriously small! I can never load all the maps I need into it and really wish I'd researched it more before I bought it. Hindsight is a wonderful thing. The 24Mb on the lastest Etrex Legend and Vista would be fine. Have to ask the wife if I can buy a new one!


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(side note: What is the difference between the listing of '# of WPs' and '# of Routes/# of WPs per route"?)

# of WPs is the number of Geocaches or other locations you can store and navigate to.


Number of routes is the number of different track logs you can store (if you want to keep a record of the paths of your journeys).


Number of points per route is the "detail" of the route. Think of them as breadcrumbs dropped along the way. The more breadcrumbs, the more detailed the route (or the longer the route) depending on whether you tell the GPSr to "drop a breadcrumb" at even distances, times, or automatically at every turn.


For a comparison of model features, take a look at Offroute.com's site.


Edit: As to memory, all of English speaking Canada except metro Toronto and Ontario is less than 56MB. New York to Philadelphia is more. Map space is a function of detail and density, not area. As with most things involving RAM, more is generally better.

Edited by Sputnik 57
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center part of north and south carolina to the ocean is about 23.8mb

fits on my sportrak color


I want the whole usa detailed on 1 sd card. how much do you think that take? 1gb or more

The whole U.S., incl. Puerto Rico, Alaska and Hawaii takes approx. 850MB using Mapsend DirectRoute NA. So, yes a 1GB SD card covers it all.

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