GPS Arcana

Okay, so yesterday I posted about a geocaching urban walk that I did, and I realized that I don’t do much gear talk on here even though I’m kind of a gear/gadget geek. You may wonder what inspired this internet outing of my inner geek? Well last weekend I had to give a GPS Basics presentation to a bunch of leaders in the local Sierra Club snowcamping group I belong to and had to brush up on the technology and fill in the gaps of my own knowledge.

In order to enlighten myself, I did the usual web surfing, but I also bought a really good PAPER book (GPS Made Easy, Fifth Edition 2008, by Lawrence and Alex Letham). Why did I choose this particular guide you ask? Because a.) the edition was published within the last couple of years—as opposed to five years ago which in electronics' years might as well be 50 years ago, and b.) the book used screen shots from my family of GPS’s: the Garmin GPSmap 60 series. The reasons I say this is a good book are that it boils the technical stuff down nicely, you don't have to start at chapter 1 even though it's a good idea to, it gives reasons WHY I might want to do something or use a feature, and demonstrates different navigation scenarios.

Now why did I capitalize “WHY” in “reasons WHY...” of that last sentence? Because the Garmin owner’s manual SUCKS. I repeat: it SUCKS! Are you listening Garmin??? It doesn’t show all of the features or screens and it doesn’t explain WHY I would want to use any of these features, or barely HOW, or what they are for, thus leaving a beginning GPS user crying tears of frustration and pulling out her hair. I’ve had this GPS for four years now and I’m STILL figuring the thing out.

In Garmin’s defense I will say this: Garmin is today—mostly—Mac compatible. And that is why I bought a Garmin. I originally bought a Magellan but made an about face when I realized I couldn’t use it AT ALL with my Mac (even today Magellan’s & DeLorme’s Mac solution is for Intel chip Mac users to run Windoz through Bootcamp—“bite me” is what I say to that). And lucky me, the Garmin GPSmap 60CSx units are still one of their most popular handhelds, so Garmin continues to put out firmware updates and compatible accessories. (Note: my unit is the 60Cx—basically the same as the 60CSx but lacking the real compass and altimeter.)

Alright so the point of this rant is not all pointless. I’m going to share with you, dear reader, the mostly Garmin-centric GPS mysteries I have unravelled so far:

• Why would I want to “project” a waypoint?

To project a waypoint is to create a new waypoint based off of another waypoint using bearing and distance. This may be handy if you are using a paper map & compass and want to create a waypoint for a location but you don't have a map with a UTM grid or don't know how to come up with the latitude & longitude coordinates for a location (hint: it takes a special map tool you can buy).

So for example, you would like to hike over to that peak labeled Pk1195 on your paper map, but it's not showing up in your GPS receiver but another nearby point is in your GPS & on the map (this will be your reference waypoint), so using the ruler on your compass you measure the distance and then take a map bearing from your reference point to Pk1195 on the map. Let’s say you got a distance of a .5 mile and a bearing of 270 degrees from your reference waypoint. Now you select your reference waypoint via the FIND button an hit enter... now you access a sub-menu by hitting MENU and select PROJECT WAYPOINT and at that time you enter the distance and bearing of your desired destination and voilé! You have a new waypoint.

Another example (this is from the book above) is if you are Search and Rescue and somebody tells you that they saw an injured person about a mile away due East. The SAR person can then project a waypoint to the estimated location of the injured person from her current location.

• Why does my accuracy suck when yours is rockin’?

I embarrassingly just figured this one out today. I had always suspected my accuracy was not as good as it could be despite having one of the more accurate consumer receivers and secretly suspected that mine was defective. I had read that in ideal conditions I should have an accuracy of about 9 feet with WAAS (Wide Area Augmentation System) activated.

Well the best I ever got was about 14 to 21 feet and often 30 to 60 feet. And last week before my GPS Basics talk I had the opportunity to play with several different GPS receivers and the Garmin Vista & ETrex were kicking my 60Cx’s butt. To add insult to injury, when on my geocache yesterday even my iphone GPS was more accurate. So I did some searching and found tonight on the Garmin support forums that if the Battery Saver option is turned on, it decreases your accuracy. OH SILLY ME! I didn’t know that saving battery power was a BAD thing?! Especially since it DOESN'T SAY ANYTHING about it IN THE MANUAL. Nice. Thanks Garmin.

This is the direct quote from the Garmin support forums:

Question: I have noticed a high EPE reading on my device since changing the mode of the unit to Battery Saver, is this a normal response to such an adjustment?

Answer: The products with high sensitivity GPS receivers will show an increase in EPE (estimated position error) while in Battery Saver Mode. An adjustment of Battery Save Mode back to "Normal" or "WAAS" modes will assist in lowering the EPE.

• What is that little D in the bar graph on the Satellite page?

I also just discovered this one today because ALL ALONG I'VE HAD BATTERY SAVER TURNED ON except for tonight when I learned that it kills your WAAS accuracy and therefor I turned OFF Battery Saver Mode (EVEN THOUGH the GPS said I had WAAS turned on in the settings menu all along *ahem*). Well now I’m seeing these little D's popping up in the reception bar graph on the bottom of the Satellite Page. And pouring through the owner's manual gives absolutely no clue as to why. Well thanks to Google and gpsfaqs.org I now know. It means my WAAS is being activated to increase the accuracy. Who woulda thunk?! Not I obviously...

• What’s the difference between trip odometer vs. odometer?

Okay I admit I got this answer from the owner’s manual glossary and then fooling around with the Navigation Page settings. It’s in theory like the difference in your car’s “tripometer” and odometer, except for the GPS's default is to reset the trip odometer AND the odometer at the same time, so the difference isn't so obvious unless you UNCHECK reset odometer. This way you can keep the odometer rolling as long as you want, but keep resetting the trip odometer when you tell the GPS to Reset Trip Data which resets all of your trip statistics.

• Why aren’t my loaded topo maps showing up?

Basically there is a map displaying hierarchy and there are sub- sub-menus you need to access in order to easily switch off which maps you want to see. You can individually switch off map sections, but if you have a lot of maps loaded that option sucks.

My story is that I have Garmin’s City Navigator maps and Garmin’s Topo U.S. 2008 maps, but I can’t view my topo maps unless I switch off the City Navigator ones. I originally was doing this individually one “quad” at a time, but when you have several quads loaded this method sucks. But there is a sub- sub-menu that allows you to switch all on or off that I stumbled upon one day. Here is how to access: go to MAP PAGE, press MENU, select SETUP MAP hit ENTER, scroll right to the “i” icon, hit MENU again, scroll down and select “Hide City Navigator”, hit ENTER. Now all of your loaded topo maps will show up.

• The hidden tide graph!

Here is a little sub- sub-menu gem. Don’t bother looking for it in the owner’s manual either. It's not there. On you Maps Page scroll to a coastline, for instance the San Francisco Bay area. There are several round icons that look like sideways blue ying yang simbols. Highlight one of those and hit ENTER. Those are little Tide Prediction Stations, and a little tide table will pop up for that location and date. You can also change the date. If you hit MENU you will get more viewing options. Play with it. It’s fun! You can also access the tide stations closest to you on the Find Page and then scrolling down to Marine Points, hitting ENTER and then Tide Stations. It will list the Tide Stations closest to you!

• The hidden elevation profile!

I thought that only the 60CSx with it's altimeter showed elevation profiles but you can view them on the 60Cx too!!! And don't expect the owner's manual to tell you about this because, just like the tide graphs, it’s not there (well it is sort of mentioned in passing, but not exactly made explicit). You have to have a route created on your GPS first to view. So make a route and on the Route Page and highlight it, hit ENTER, now hit MENU, on the list scroll down and select “Profile”, hit ENTER and then select which elevation data the GPS should use, and POOF! an (estimated) elevation profile for your route appears. Hit MENU again and you can control the exaggeration and length

Okay that was a long blog posting, but hopefully somebody somewhere will find it useful. As I make new discoveries, I will post them.