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Archive for the 'GPS' Category Page 3 of 25

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Satellite Tracks And Visibility In Google Maps

Published by
Leszek Pawlowicz
 in GPS. 3 Comments

The Live Real Time Satellite Tracking page lets you select a satellite, or groups of satellites, and plot their position in a Google Maps interface. You can select all types of a particular satellite currently visible from your location, and plot them along with the satellite’s visibility footprint (Iridium satellites here):

iridium

The graphical view updates in real-time, so you can see the satellite’s position change. A display shows you the current visibility parameters for the selected satellite:

2010-11-06_194014

You can select from lists of satellites with a single click:

2010-11-06_193947

And then select from a list of satellites (GPS operational here) to choose which one to track.

2010-11-06_194128

Clicking on the satellite name brings up additional info about the satellite:

navstar

With the “Up In Your Sky” links, you’ll have the option of selecting multiple satellites, including all of them in a particular category.




Online GPS Satellite Geometry Error Predictions

Published by
Leszek Pawlowicz
 in GPS. 2 Comments

Two of the factors in determining the accuracy of your GPS positions measurement are how many GPS satellites are visible from your location, and how evenly distributed over the sky they are. Generally, the more satellites that are visible, and the more evenly they’re distributed, the more accurate your position. This is expressed numerically by a parameter called the Dilution Of Precision, DOP for short; the smaller the DOP, the more accurate your GPS position is likely to be.

A few consumer-grade GPS receivers will show you the current DOP; more advanced commercial models can show you a predicted plot of DOP over the course of the day, useful in figuring out the best time to get an accurate position measurement. I’ve posted previously about the free Trimble Planning software, Windows-only software that can generate plots showing the change in DOP over the course of a day. For non-Windows people, there’s now a limited online tool from Ashtech (formerly Magellan Pro) called Web Mission Planning that can provide you with some of that information.

Select your desired location from the first screen – it defaults to your current IP address’s location.  Elevation Mask sets the minimum altitude that a GPS satellite needs to have to be considered in the calculations, a simple way to account for sky blockage by objects like trees and buildings. There’s also a “Local Mask” tool at the bottom that lets you fine-tune that blockage to account for individual objects:

wmp1

You then select a single date, a start and stop time during that date, and which satellites you want to use for the calculation: GPS (the US system), GLONASS (the Russian system, not used by most GPS units), and SBAS (the WAAS/EGNOS real-time correction system). You’ll then get your choice of four plots, some with interactive components.

1. The total number, and ID numbers, of satellites visible at any time (interactive; move the cursor over the plot to get more info):

satellitecount

2. A similar plot, but with DOP plotted in colored lines:

dop

3. A polar diagram that shows the satellite positions in the sky; change the time interactively by moving the slider at upper-left:

polar

4. A Google Earth plugin view that shows the satellites and the line of sight to your location; a time animation control runs through the entire specified time duration. Fun to watch, but not terribly useful:

gegps

Biggest problems with the site are the cluttered diagrams, and the inability to print or output the data into a more convenient format for use in the field; the only option for the latter is to do a screen capture. So if you already have a copy of Trimble Planning software, you can probably skip this site; that program has better controls, and more output options. But if you’re not running Windows, or don’t have access to Trimble Planning, the Web Mission Planning site might be a useful alternative.

Via GPS Tracklog.




Displaying GPS Data On A Website

Published by
Leszek Pawlowicz
 in Google Maps, GPS, GPX, KML and Web apps. 10 Comments

Got an email a few weeks ago from someone who wanted to post data taken with a GPS, in GPX file format, and display it as an embeddable map on his blog; he couldn’t find anything on that on the web. I offered one possibility, and he in turn suggested that I might put up a brief post on the topic. Here’s a few ways to do it, off the top of my head.

Some of these will require you to convert your GPX data into an alternate format, like KML or shapefile. A search of this website will bring up lots of programs that can do these conversions, but probably the simplest way is to load your GPX file into Google Earth, then export the data in KML or KMZ format. Note: All of these sites require you to create a free account.

Google Maps My Maps – The alternative I suggested; not a lot of features, but very easy to use. Import KML/KMZ files from your computer or a web link, use the built-in editor to add additional features. You can then display the map on your website using a widget.

Google Docs Spreadsheet – If you convert your GPX files to CSV files using a program like DNRGarmin or GPXToPOI, you can import the data into a Google Docs spreadsheet; Google offers a tutorial on converting that data into a KML network link for display in Google Maps or the Google Earth plugin.

GeoCommons – Just posted about this yesterday; upload your data and display it in widget format. All data you upload will be available for anyone to use or download.

MapChannels – Lots of map creation features, and embeddable maps.

ScribbleMaps Pro – Similar to Google Maps My Maps, but offers lots more import options and drawing tools. Highly recommended.

Feel free to add your own recommendations in the comments section.




Embed A QR Position Code Losslessly Into A Geotagged Picture With QRStamper

Published by
Leszek Pawlowicz
 in geotagging and GPS. Closed

Mike Lee’s QRStamper program will losslessly embed a QR code with the coordinate data for a geotagged photo into a copy of the photo. Just drag and drop the photo onto the program icon, and in the same directory as the original, QRStamper will create a copy of the photo with the QR code embedded at lower right:

2010-09-26_17-33-27_591-QR

Scan the QR code with an app like Android’s Barcode Scanner, and retrieve the geotagging coordinates:

qr_capture

The similar GeoStamper program embeds a standard geotagging icon losslessly into a photo copy, to indicate it’s geotagged:

untitled-1-geo

His GPStamper program, covered here a long time ago, which losslessly embedded actual coordinate/location data into a photo, is no longer free. However,  it still has a 30-day free trial, and “non-commercial scientific research or survey use is eligible for a free licensed version.”




Crowdsourcing And Coordinating Data Collection With Handheld GPS Units

Published by
Leszek Pawlowicz
 in data, GIS, Google Earth, Google Maps, GPS, KML, MapWindow, shapefile, spreadsheet and Web apps. 5 Comments

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

Published by
Leszek Pawlowicz
 in Garmin and GPS. 2 Comments

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.

Note: See comments section for Joel’s info on updates/fixes.




New Android-Related Website: AndroGeoid

Published by
Leszek Pawlowicz
 in Android, blogkeeping and GPS. 1 Comment

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

Published by
Leszek Pawlowicz
 in Android, Garmin, GPS and Magellan. 6 Comments

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.




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