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Archive for the 'GPS' Category

Crowdsourcing And Coordinating Data Collection With Handheld GPS Units

Got an email today from someone with a data collection/coordination/assembly problem. They have multiple people out in the field with Garmin GPS units recording data, and bringing it back to a central location for collation/combination when they’re done. Since Garmin GPS units have limited capabilities for data storage – coordinates, name, comment, date and time, elevation, and that’s pretty much it – additional data associated with a point has to be recorded by hand. Once back from the field, data has to be downloaded from individual units, associated with the additional attribute data from forms, all the data combined together into a single dataset, then converted into GIS-friendly format. And the process they had come up with wasn’t really working well for them.

I think this highlights some of the major limitations of classic stand-alone handheld GPS units. They’re really designed for us in personal data collection, not combined data collection; assembling data from multiple units can take a lot of work. Plus, their limited data collection capabilities require offloading data attribute acquisition to other formats (e.g. pencil and paper), adding the addition problem of associating that data with coordinates later on. There are lots of professional solutions for these problems, like Trimble or MobileMapper GPS units, Terrasync and ArcPad software, but these can be complicated and expensive. I challenge you to find anyone with enough patience to use Terrasync for a single day without swearing at least once; I know I can’t  ;-).

For a few years, I’ve had CyberTracker on my list of potential topics to post on. CyberTracker is a terrific data acquisition and collation tool for field data with tons of great features, like custom data acquisition form design for easy data entry, moving maps, easy data collation and conversion to GIS-friendly format. Plus, the software is free, and the hardware is (relatively) affordable. But unfortunately, I think time and technology are passing Cybertracker by:

  • While the central data software runs on Windows, the field data collection software runs on old-school Palm OS and Windows Mobile. Palm OS is dead; Windows Mobile development has stopped with version 6.5, and only maintenance updates are scheduled. So the useful lifetime of any data collection system built around CyberTracker is limited. If you need a fast/cheap/short-term solution, CyberTracker is free for non-profit use, and you could probably pick up the hardware very cheaply on eBay. Long-term, I don’t see it having much of a future in its current form.
  • The data collation model is also becoming obsolete. With CyberTracker, you have to bring all the data units to a single data download/collation computer. While there are still places in the world where this might make sense, an increasingly-connected world means that data download/collation to the cloud instead of an individual computer makes more sense.

I’m really excited about the possibilities for crowdsourced geographic data collection and collation using portable devices running Android OS (yeah, iOS too). There are already several interesting apps for doing this, and I hope to cover some of those soon on my AndroGeoid website. And I suspect that the small number of apps that can currently do this will be quickly joined by far more apps, and far more capable apps, in the very near future. But that doesn’t help with my emailer’s current problem. I suspect there are many different ways you could do this, but here’s the first approach that came to me using all-free software and services.

1. Make sure that everyone on the project has a Google account (i.e. Gmail); completely free.

2. Have the project leader created a single main data spreadsheet on Google Docs, with all the desired data attributes (e.g. point name, coordinates, comments, additional data fields from the paper forms, etc.) and share a link to that spreadsheet with other project members so that they can edit it as well.

3. Project members can download data from their Garmin units using DNRGarmin, and then export the data from DNRGarmin in CSV format.

4. Load the data into the spreadsheet program of your choice, and add/edit data from data forms to make it conform to the data structure of the main Google Docs spreadsheet.

5. Copy the data cells in the spreadsheet program, and paste them into the main Google Docs spreadsheet. Note: Use Ctrl-C and Ctrl-V to copy and paste cells into Google Docs instead of using the Google Docs Edit menu to perform those operations, as the latter doesn’t seem to work for pasting data from different applications into Google Docs. You no longer have a single computer as a choke point for data entry; multiple people can add data to a spreadsheet at the same time, and Google Docs will coordinate data entry so that nothing is lost. And if you save the spreadsheet data from steps 3 and 4 as separate files, you’ll have backup copies of the original data as well.

For those who aren’t comfortable with working with spreadsheets, Google Docs lets you set up a “Form” to let anyone add data to a Google Docs spreadsheet directly; however, this increases the chances of coordinate data entry error.

6. Now that you have all the data centralized in Google Docs, you have lots of flexibility in how you can handle it:

  • Export the data in CSV format, and you can then import it into any GIS program that supports CSV data. If your GIS program doesn’t, use MapWindow to convert your CSV file into shapefile format first.
  • Unlike shapefile attribute tables, where adding/removing/re-ordering attribute data columns can be a pain, you can easily perform those operations in Google Docs and then re-export the data in CSV format.
  • Convert the data directly into a continuously-updated KML network link for display in Google Earth or Maps using Google’s Spreadsheet Mapper tool.
  • Use any of Google Docs built-in tools to analyze/plot/sort/visualize data, including their way-cool Fusion Tables.
  • And I’m sure there are more options I haven’t thought of.

Know an alternate approach? Have any additional ideas?  I welcome your links and suggestions in the Comments section below.




Easy Conversion Of GPX Files To Garmin Format With GPX2IMG

Joel emails to announce that his GPX2IMG program is finally ready for official release. GPX2IMG imports standard GPX data files (tracks and waypoints), lets you edit them, converts them to IMG Garmin-compatible format, and even installs the map file into MapSource or BaseCamp for easy upload to your Garmin GPS unit. The program isn’t fully free; regular price is $20 (available for $13 until 9/23/10). However, the demo version will let you import up to two GPX files, edit them, convert them to .img format with a watermark, and even install them in MapSource; the registered version removes the file limit and watermark.

Interface is clean and simple; load in your files and view the data in a map window. GPX2IMG lets you select waypoints and tracks, edit their names and other info, and set their appearance to standard Garmin point/line types:

gpx2imgscreenshot

You can’t modify the actual track point data itself, nor can you move a waypoint/POI. You can create a waypoint by double-clicking the map area, but the inability to set the specific latitude/longitude of  that waypoint is a drawback. You can use custom TYP files to create your own linestyles; instructions are in the comprehensive help file (and there are videos on the GPX2IMG website).

Once you’re done with adding/editing data, set the desired parameters in the Preferences window:

preferences

Then click on the “Convert Checked Files” button to start the process. In the unregistered version, you’ll have to wait 15 seconds. GPX2IMG will compile the GPX data into a .img file, and then install it for use in MapSource or BaseCamp for uploading to your Garmin:

MapSource

A few minor issues:

  • A waypoint file of mine didn’t import successfully; I’ve passed it on to the author, and I assume that issue will get fixed shortly.
  • You can only have one GPX dataset created by GPX2IMG loaded into MapSource/BaseCamp at a time; I would hope this will change, as that really is a major drawback.
  • You can’t uninstall the mapset from within the GPX2IMG program; you can use a separate program like MapSet Toolkit to do this, but I’d like to see that option directly within GPX2IMG.

You can create your own Garmin map from GPX files using fully-free tools; see my many-part series on Tools For Custom Garmin Vector Maps. Doing it yourself is more complicated, takes longer, and there’s a steep learning curve, but you’ll have more flexibility in the final results. But if you want to bypass those complexities, and just quickly generate simple Garmin map files from your own data, GPX2IMG works and is easy to use. Even the limited demo version has enough utility to make it worthwhile.




New Android-Related Website: AndroGeoid

After my previous two posts on Android, you might expect to see posts on Android-related topics showing up here at Free Geography Tools. That was my original plan, but I’ve decided that Android is a distinct-enough topic to warrant its own website. So, I’m announcing my new Android-specific website, going online today (8/18/10): AndroGeoid. There, I’ll cover apps and topics related to using Android hardware and software to explore, measure, record and map the world. This will include obvious geography-related topics, like apps for :

  • GPS
  • GIS
  • Map displays
  • Compasses
  • And so on …

But the website’s focus will range well beyond that, to topics that encompass some of Android’s more unique capabilities;

  • Geographically-related Augmented Reality
  • Location-linked online information resources
  • Crowd-sourced data collection
  • Measurement apps that take advantage of Android’s sensor suite (accelerometers, orientation, magnetic field)
  • Applications for recording full sets of information linked to location: Coordinates, direction, orientation, notes, photos, videos, sound, panoramas, augmented/virtual reality, and more.
  • And other cool stuff …

The Android world is currently dominated by smartphones, connected wirelessly via 3G to the Internet, and I’ll cover apps that take advantage of that. But the ecosystem is likely to expand very soon to models that only come with WiFi connections, and even with smartphones there will be times when no connectivity is available. So, I’ll also cover apps that work with non-connected stand-alone Android devices.

And the name, AndroGeoid? Well, GeoAndroid  was already taken ;-). But AndroGeoid works for me: the geoid is:

that equipotential surface which would coincide exactly with the mean ocean surface of the Earth, if the oceans were in equilibrium, at rest, and extended through the continents …

So sayeth the almighty Wikipedia. In other words, all things geo-related to Android will flow downhill to the AndroGeoid.

The first couple of posts may look familiar – they’ll be slightly revised versions of the posts I’ve done this week on Android. New material should start showing up on Friday. Plus, I’ll have a brief weekly listing/recap of AndroGeoid posts on this site, usually on Fridays.

And in case you were wondering, I still expect to post regularly on the Free Geography Tools site at about the same frequency as I have been, about 4 posts a week. Hopefully, I can keep both sites up and running at the same time. Not unrelated, I’ve got a new Guest Post page up ;-).




Android: The Future Of Consumer GPS – Part II

After yesterday’s magnum opus about how Android will transform the consumer GPS industry, today’s shorter post is a few random thoughts on how the big three handheld GPS makers might be affected by Android, and how they might respond. Personally, I think it’s going to be tough for them to adapt. Up until recently, handheld GPS units have been a fairly limited specialty market, allowing manufacturers to control interfaces and map data, and charge exorbitant prices due to limited competition. In most consumer electronics fields, prices drop even as capabilities increase; that really hasn’t been the case for handheld GPS. Android has the capability to turn GPS into a commodity market, meaning less control and more competition, leading to lower prices. And this is an environment that the old-school GPS vendors may have trouble with.

Magellan: Magellan is still struggling to overcome the disastrous premiere of their Triton line in 2008: decent hardware with capabilities unique at the time (raster imagery, 3-axis compass) sabotaged by horribly buggy software. Most of these problems got fixed, but too late to make a difference. Magellan was acquired late in 2008 by MiTAC (parent company of Mio, and they’ve just recently announced a new series of Explorist models, due out this fall.  For standard GPS models, the specs on these look pretty good, and the prices are very competitive. But in the long run, I don’t see how they can compete with more-capable Android models that are likely to sell in the same price range or even lower.  Putting someone else’s Android unit into a Magellan body with a better antenna and waterproof/field-rugged design might be a better way to go. They already have some experience using that approach with their new case for the iPhone, which enhances the iPhone’s GPS abilities while offering better protection against the elements; they just have to do it more cheaply.

DeLorme: DeLorme has moved into second place for handheld GPS units with their PN series, the first consumer models with raster/aerial imagery, and the first models with an affordable subscription plan for this imagery. They’ve also come out with a new model recently, the PN-60, with an upgraded interface and the ability to interface with SPOT communicators for satellite text messaging. But $400 for a GPS with a 2.2” display? No touchscreen? No apps? Their $250 xMap software lets you upload GIS data (raster and vector) to their PN models, but you can already put raster imagery on Android models, and GIS vector data can’t be too far behind. I don’t see this proprietary hardware line as having much of a future, and they don’t have much experience with alternative hardware.

Garmin: Garmin seems to develop an OS for their GPS units, and then use it as long as they can. The OS developed for their eMap model in 1999 was adapted and upgraded for most of their handheld models through 2006, culminating in the classic 60/76Cx series. These were probably the best-selling handheld consumer GPS series of all time, and four years later are still among their most popular units. They’re only 2.5 years into their next-gen GPS OS, the one that powers the Colorado/Oregon/Dakota/62/78 series, and they’ve certainly released a ton of variant models in these lines. The question is whether they can move past their own proprietary hardware and software designs and move quickly to an Android platform, using their strong GPS expertise to bring additional features that will differentiate their models from the rest of the market.

I’d like to think so – I’ve been a Garmin fanboy for 10 years now, and even now that I own a Droid X, you’ll have to pry my 60Cx out of my cold dead hands. But their recent history isn’t encouraging. Their first attempt to move Garmin technology to a cellphone platform, the nuvifone, was universally despised by reviewers. Their second effort, the Garminfone, was based on the Android platform, and received much more favorable reviews; the car navigation software of the Garminfone is generally considered to be the best Android car navigation system so far. If the phone had come out in the latter half of 2009 as originally scheduled, it could have been a huge success. But instead, it was first released in June 2010, and was crippled by:

  • Older software; it ran Android 1.6 when every other phone being released at the same time ran Android 2.1
  • A custom interface that makes it very difficult to upgrade to more recent Android versions
  • Slow processor
  • 3 MP camera
  • A screen pixel count 1/4 of its similarly-priced competitors, and a smaller screen
  • Garmin car navigation software on competing models that, while not as good, was free
  • Lousy battery life
  • No headphone jack

In short, simply not competitive with other Android phones. A month-and-a-half after being introduced for $199.99, it was already discounted by $70, and was part of a “buy one, get one free” package from T-Mobile. Even with that, it’s only sold about 20,000 units, which Garmin themselves acknowledged as a disappoint performance in their latest quarterly report..

If Garmin is going to survive in the consumer market, they’re going to have to move faster than that in developing products. And they’re going to have to give up control of the overall interface in favor of Android’s standard, putting their interface into just their applications. And they need to leverage their GPS engineering capabilities and map data into advantages that make  their units stand out. If they don’t, they’re going to have a tough time surviving in this new market.




Android: The Future Of Consumer GPS – Part I

I’ve owned a handheld GPS ever since the first “consumer-grade” model, the Motorola Traxar, was released in 1993: $900, 6 AA batteries, 8 satellites max, could only record waypoints, and about the size and weight of a brick. Man, was that an awesome GPS unit! I’ve upgraded several times since then, and am glad that handhelds have improved as much as they have. But I’ve always chafed at their restricted ability to record information out in the field: waypoints with a name and short description, tracks with a name, and that’s pretty much it.

Back in January, I posted my “wishlist” for a field-ready GPS unit;  I had hoped that the newer Garmin Oregon models might satisfy most of those requirements, but a lousy touch interface makes those units too difficult to work with. I tried to put together a “field-ready” semi-rugged Windows netbook that met most of my needs, but the poor screen visibility in sunlight conditions was just too great a restriction on its use; while still handy to have, full utility required either shade or a cloth draped over my head. I had pretty much given up on finding what I wanted, and was about to buy one of the new Garmin 62-series GPS units as an upgrade from my trusty Garmin 60Cx; nowhere near all the features I wanted, but enough extra ones (aerial/raster imagery, three-axis compass) to justify the purchase.

A recent upgrade in local cellular antennas finally let me dump my landline phone, and move over to a full-time cellular connection. As part of that process, I decided to pick up an Android smartphone, specifically a Motorola Droid X. While I knew it came with a GPS, that wasn’t the primary reason for getting it – I just wanted a phone that would allow me to stay connected to email and Internet when I was out and about. But having used it for a few weeks now, I’m now convinced that GPS-capable Android-powered units, phones or otherwise, are going to completely transform both the handheld and automotive GPS markets.

Here’s a comparison of my Droid X with the comparable top-of-the-line Garmin unit, the Oregon 550. Bold text indicates which unit IMHO has the advantage in that category.

Motorola Droid X Garmin Oregon 550 Comments
Price $569 list $499 list The Garmin is often discounted by about $100; the Droid X currently isn’t, but will likely drop dramatically in price over the next six months. This doesn’t include cellular plan costs.
Weight 6 oz. 6.8 oz.
Processor Speed 1 GHz 200 MHz (?)
Storage RAM 8 GB 2 GB
microSD expansion Comes with 16 GB, can take up to 32 GB Comes with none, can take up to 4 GB
Display size 4.3” diagonal 3” diagonal
Screen Resolution 480 x 840 240 x 400
DPI 240 157
Color Depth 16 (24) 16 Droid X screen is 24-bit-color capable, but some specs indicate that the OS is only displaying 16-bit color
Daylight Screen Visibility Good Very good Biggest problem with Droid X screen is glare; screen protector helps with that.
Shade/Indoor Screen Visibility Outstanding Very good
GPS Satellites 12 12+ Unclear from specs
WAAS/EGNOS No? Yes Unclear from specs
Assisted GPS Yes No Network signal reduces TTFF
Three-axis compass Yes Yes
Camera 8 MP 5 MP
Multiple camera modes Yes No Droid X has standard, macro, panorama, plus multiple exposure controls
Video Yes – 720p HD No
Barometric Altimeter No Yes
Calculator Yes Yes Droid X has advantage because you can download and install multiple calculator apps
Touchscreen Yes; multi-touch capacitive Yes; resistive A draw; multi-touch is useful, but resistive can be used with gloves on
Keyboard data entry Yes; multiple QWERTY keyboards available, some with text prediction Yes; A-Z keyboard You can choose your preferred data entry mode with the Droid.
Voice-to-text data entry Yes, with wireless connection No
Voice recording Yes No
Text data limits Limited only by unit’s memory Limited by waypoint data fields – about 80 characters
Wireless connectivity WiFi; 3G; Bluetooth Proprietary wireless interface With a Garmin, you can only transfer wireless data between compatible units
Battery life 5-6 hours (?) 16 hours For Droid X, depends on screen brightness, whether you have the wireless connections on, etc..
Field-rugged No Yes Garmin is IPX7-waterproof
Built-in maps Yes Yes Garmin has baseline vector map; Droid has Google Maps
Free up-to-date online maps and POI data Yes No Garmin’s detailed vector maps have to be purchased; updates cost extra. Droid has access to continuously-updated maps for free, but these typically require the unit to be online.
Offline raster maps Yes with third-party apps Yes with Garmin Custom Maps, BirdsEye subscription
Offline vector data Yes with third-party apps Yes with free/paid Garmin maps Garmin data ecosystem still far superior here.
Car navigation Yes (free, but requires wireless connection) Yes (requires paid Garmin maps) Draw; Droid has voice, 3D navigation, but requires wireless connection; Garmin works offline.
Waypoints, tracks, routes Yes with third-party apps Yes Droid third-party apps give you more freedom with what you do with the data
Geocaching Yes with third-party apps Yes
Ability to add additional applications YES NO

I could go on, but just from the above, the Droid X is at least competitive with the Garmin feature-wise, and you could easily make the argument that overall it’s far superior. The few categories where the Droid X falls short (WAAS, ruggedness, battery life) can be partially remedied with add-ons: you can use it with a WAAS-capable Bluetooth GPS transmitter, spare batteries are cheap on eBay, and cases offer some level of physical protection. But more to the point, they are due to the Droid X being designed to be primarily a cellphone, not a GPS unit. It really shouldn’t be hard at all to design a unit that remedies those failings, and sell it at a  reasonable cost.

Here’s a link to a mil-spec ruggedized Android GPS unit already available; currently costs $1200, but divide that by the factor of 3-5 that military contractors typically add on and you’d have a reasonably-priced consumer unit. Less-expensive consumer Android models with GPS are on the way, like the Samsung Yepp at about $350, or this Archos mini-tablet for $150; it’s not that big a stretch to think that fully field-qualified versions of those units could be made and sold fairly cheaply. And I’m especially intrigued by the Notion Ink Adam, an Android-based tablet due out late this year or early next year. The Adam will be offered with an optional 10.1” Pixel Qi LCD screen, which can be switched from a standard transmissive LCD mode to a sunlight-visible transflective color mode, and then to a low-power black-and-white e-Ink-like mode. With  GPS, WiFi, 3G, and built-in camera, this model will sell for $498, or less than a Wifi-only iPad.

But hardware is only a small part of Android’s advantage; the big advantage is that you can put applications onto an Android unit to add functionality, something you can’t do with standard Garmin GPS units. There are already hundreds of position/geography/location-aware apps available for Android units, and that number grows every day. There’s currently only a very limited number of GIS-related apps, but I’d be surprised if many more of those don’t show up soon. And even with the limited number of apps currently available, you can already do far more with an GPS-equipped Android unit than with a standard handheld GPS. Given the impending death of the classic Windows Mobile platform, the primarily OS for many portable GIS and data acquisition apps like ArcPad and Terrasync, it would make sense for companies like Trimble and Ashtech to look at Android as a viable platform for future hardware and software development.

I suppose that the Apple iPhone/iTouch/iPad/iOs ecosystem could be a viable alternative to Android-based models – the hardware and software are certainly good enough – but I doubt it will be. Anyone can license the Android OS and create a hardware device that uses it, which means more models, more competition, and lower prices. Apple has firm and exclusive control of all hardware that runs iOS, which means fewer models and higher prices. I think they’re repeating the same mistakes that resulted in Windows dominating the PC market, but whatever; at least for now, it’s a lucrative market for them.

All for now – a few more random thoughts tomorrow.




Free Tools For Custom Garmin Vector Maps XVIII: Full GUI For mkgmap Compiler

Took a while, but this is the final installment of my epic 18-part series on free tools for making custom Garmin vector maps. I covered the free map compiler mkgmap in part 13, which converts OpenStreetMap data files (.osm) and Polish map files (.mp) to Garmin’s binary .img format. It’s command-line only, which can make it a pain to use. I wrote a simple Windows GUI for it a while back, but it wasn’t very good:

  • It required the compiler to be in the same directory as the data file.
  • It only worked for .osm files, not .mp files.
  • It assigned every compiled map the same default Map ID number (63240001.img), which meant that you could only use one compiled map at a time without having map conflicts.
  • It didn’t allow use of any of mkgmap’s more advanced options.

I’ve finally gotten around to fixing some of these issues, and now have a newer version of the GUI available; download it here (it comes with a copy of the mkgmap compiler), and unzip it into the folder of your choice. You’ll need to have Java 1.6 installed on your system; which you can check at the Java website. Run the executable:

supermkgmapgui

Use the button at upper-right to select the .osm or .mp file you want to compile. Hold the mouse cursor over each of the variable options to see pop-up help text describing their use, derived from mkgmap’s original documentation. The most important variables in the General Options section are:

  • Map ID Number, which should be a unique integer value between 65536 and 99999999 to avoid conflicts with other maps
  • Description, which identifies the mapset in the GPS unit

The other General options don’t seem to make that much of a difference.

Optimization options include Reduce Point Density with the Douglas-Peuckel algorithm to shrink the map size and speed up display; default is 2.6, and higher values simplify even more (mkgmap’s author recommends 10 as a good value). Turning Merge Lines on attempts to merge features together to simplify a map; haven’t noticed it making that much of a difference. For miscellaneous options, Draw Priority determines in what order vector maps are drawn; higher values mean the map is drawn later, on top of maps with lower values, obscuring those maps completely. Transparent maps have the higher priority of all, but you can see all parts of the vector map below them that aren’t obscured by the features in the transparent map (like a clear overlay on top of another map).

Once the options are set, pressing the “Compile” button creates a batch file called “compile.bat” that is then executed to compile the map code into the binary .img Garmin format; you should find the resulting file in the same directory as the map code file. Opening the “compile.bat” file in a text editor will show you the command line usage of mkgmap, and you can modify it there for further use if you like. You’ll find the compiled map in the same directory as the original map code file, with a filename that’s the same as the Map ID Number, and the file extension “.img”. See other posts in this series for info on how to upload this file to your Garmin GPS unit.

Reset” clears out the option values, “Help” takes you to this blog post, and “Exit” does what you’d expect.

This isn’t the full set of options supported by mkgmap; I’ve left out all of the routing options, and a bunch of others associated with creating full mapsets. I may wind up slowly adding some of those options on in the future, but this version should be good enough for basic map compilation. As usual, use at your own discretion/peril, and report any bugs to me.




Geotagging Coordinate Viewer For Adobe CS5

Adobe has released a free  plug-in for applications in their Creative Suite 5 (CS5) (e.g. Photoshop, Illustrator) that adds a “GPS” tab to the info window:

It doesn’t do a lot, just display an image’s embedded geotagging information in it, but it’s better than nothing. Available for both Windows and Mac.

From DPreview, via OgleEarth.




Handheld GPS Units – Beyond The Manual

It’s no secret that the manuals many GPS makers puts out with their handheld GPS units aren’t always ideal. They can be very confusing, give cursory explanations of more complicated functions, and often leave out any mention at all of advanced functions. Plus, as firmware gets updated and features get added/dropped, the printed versions become out-of-date, and even the online PDF versions lag in adding descriptions of new features. Here are some online resources to help plug the info gaps for these units.

GPSFaqs.Org: Contains comprehensive FAQs for the following Garmin models -

If your eTrex model or GPSMap isn’t listed above,  you may find the answer you’re looking for in the FAQ for a different but comparable model, since most of these models share a similar OS/interface.

GPSFaqs.Org also has FAQs for Magellan GPS units; coverage is strong for Explorist models, but cursory for Triton models.

Yahoo Groups: A number of active groups for the GPSMap series (60Cx/60CSx and 76Cx/76Cx), as well as eTrex models (general and the Legend). Not a lot of action in the Triton or DeLorme forums.

Groundspeak GPS And Technology Forum: Free registration required. Regular postings/discussion on GPS units from a variety of manufacturers, mainly Garmin and DeLorme.

DeLorme Community Forum: Probably the best source for info about the DeLorme PN series of GPS receivers.

TritonForum: By far the best source of info for the Magellan Triton series.

GPSFix Wikis: Created by Scott at GPSFix.Net, an exceptionally strong resource for info about modern Garmin units in the following series:

gpsinformation.net: Tons of general info about GPS, and pages about specific units from a wide variety of makers, some dating back to the 1990s! May take a bit of hunting to find the info you’re looking for.