Geocaching Take 2

The major problem when I tried to use Mio C230 to find geocaches is that by default the static navigation is turned on. What is static navigation. Murphyfields has found a great link about static navigation. Here is the quote about static navigation from SiRF.

93. Explain the static navigation parameters.

Since SA was turned off, we now disable static navigation as our default, and we recommend that you do also. When it is enabled, if velocity is below 1.2 m/s for 3 seconds we will freeze the position, and leave them frozen until velocity exceeds 1.4 m/s (so there is a bit of hysteresis in the solution).

123. What criteria are used to enable and disable the static navigation filter?

Static navigation is a mode designed for motor vehicles, which causes the position to become pinned at one location when velocity is determined to be low enough. This is designed to make navigation systems operate more reasonably when the GPS Selective Availability (SA) signal degradation is turned on. When the navigation software determines that the vehicle velocity is less than 1.2 m/s for 3 seconds, the position is pinned to its current position. It remains pinned until either velocity is detected above 1.4 m/s, or position is computed to be 200 m from the pinned location.

This explains why the NoniGPSPlot stopped working (frozen) when I used it on foot. To disable static navigation, you need a utility called SirfTech. You can download it from here. Create a directory called SirfTech under ScriptPrograms and put SirfTech.exe in it. You can use FileMan CE to run it or create an entry on the desktop. Please refer to this post if you don’t know how to add it to the desktop. I have also created an icon file for it.

SirfTech is a powerful and complicated utility. I wish there is an easier way to toggle static navigation, but there isn’t. I will tell you a bit about how to use SirfTech to disable static navigation. Please note that, DO NOT RUSH on doing these steps. Wait for a few seconds before do the next step.

The first time you run SirfTech, you need to set the com port. Click on Com. Set the Comm Port to COM2: GPS_COM . Baudrate to 4800. Click on Open. Wait for a few seconds to let the program connect to the GPS. Click on OK.

Now, we need to switch to SiRF mode. Click on Nmea and then Set Serial Port (Switch to SiRF). If the Baudrate was not set, set it to 4800. Click on Set and then OK.

We can now disable static navigation. Click on Sirf and then Static Navigation. Uncheck the Static Navigation checkbox. Click on Set and the OK.

Before you run other applications, it’s better to return the GPS to NMEA mode. Click on Sirf and select the last opiton Switch to NMEA Protocal. If the Baudrate was not set, set it to 4800. Click on Set and then OK.

Whew! That’s quite a few clicks to disable static navigation. Now you can exit SirfTech and start your GPS application.

When I first attempted Geocaching, I used NoniGPSPlot. I didn’t like it. I used MioMap this time. I entered the geocaches’ coordinates into MioMap using DegDec format. (In MioMap, do: Map -> Menu -> Coordinate) You can find the coordinates in DegDec format when you click on other conversions on I then added these location as POIs.

With these preparations, I was able to find our very first goecache! Yea!

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  1. Murphyfields,

    Thanks. Yes, I definitely would try again. I have a question for you. When you get to the location indicated by your GPS, can you find the cache right away? Is the coordinate accurate? Some caches are hidden really well. I wonder how big of area should I search for it.

  2. Most are pretty close to the listed coordinates, but I think the best accuracy of a GPS you can expect is something like +/- 6 to 10 feet. So combining the uncertainty of the original coords and your own GPS, it works out to something like 10 to 15 feet. I think I usually get closer than this, but not always. Usually on the easy ones there is something obvious nearby that draws your attention, like a tree or stump or pile of rocks. But in canyons or under tree cover, you could be off by 50 feet or so.

    It’s a good idea to check out the find logs. There people may say it was right on the money, or that it was way off to the northeast. If many people struggle to find it, you probably will too. Just beware that some of the logs might say something like “I never would have thought to look at the white pipe connected to the gas meter. It looked so real.” and that can destroy the fun of the search. Usually they are more discrete.

    Good luck and have fun.

  3. How was the battery life of the c230?

    I’ll be picking up one just for fun since they are on sale at Radio Shack this week for half off.

  4. Murphyfields

    After I disabled static navigation, I didn’t enable it again. MioMap is working OK with static navigation disabled.

  5. I read somewhere that it really does not help much now that selective availability has been turned off. And I don’t know if the government will ever turn it back on…hopefully not since that would probably imply a time of war.

    Thanks for the info

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