This is a topic that was recently discussed elsewhere, but I thought I'd mention it again. If you have one of the now vintage Magellan handheld GPS receivers such as the SporTrak, Meridian, or eXplorist units that will accept a "User Grid" projection and will display those User Grid coordinates as the main coordinate system of the display, you can configure the receiver to display State Plane Coordinates in whatever length unit you wish.
Here's a link to a page that explains how to do it and that gives a link to a spreadsheet with the various projection parameters you'll want to use.
State Plane Coordinates with a Magellan handheld GPS
Note that only one User Grid projection can be stored at a time, so if you change zones, the new parameters need to be entered. This takes just a couple of minutes.
The 2004-vintage Magellan SporTrak I use is WAAS-enabled and generally displays NAD83 coordinates in the Texas Coordinate System that are generally accurate within about 7 ft. in Northing and Easting. Part of that is the systematic offset between ITRFXX and NAD83(CORS96), i.e. the handheld is really returning ITRFXX coordinates, not NAD83. I haven't made a careful test of this or bothered to figure out what minor adjustments to the projection parameters would minimize the offset effect since for corner search if I can navigate within about 7 ft. of a corner in a rural area, I can find it and many of the 19th century surveys have errors in them larger than that anyway. A more industrious person could fine tune things.
The other feature that is exceptionally useful is setting up the navigation display to show crosstrack error on a route. To walk a line between two points, the coordinates of the points are entered as waypoints for a route and the route is activated. That is also exceptionally useful for recon and search.
It isn't clear whether any of the current generation of inexpensive Magellan handhelds allow the use of the User Grid projection feature in this way. I understand that the Tritons, for example, do not. This may well be a case of the older technology actually serving the purpose better than the new. I discovered that one can still buy new SporTraks on the internet for about $125.
I'm trying to work out something similar with my iphone. the "GPSkit" application has a way to upload waypoints. It seems that most users are running or biking and sharing trails, but it might just work. I was hoping to play around with the uploader today, but have to finish some maps first.
I have a Garmin 76S that I did a user defined grid on a while ago, but I haven't used it much, might have to dig that out too.
Lambert User Grid Projections
> I have a Garmin 76S that I did a user defined grid on a while ago, but I haven't used it much, might have to dig that out too.
As I recall (from about six years ago, though), the Garmins would handle user grid projections as long as they were Transverse Mercator. They weren't configured for One or Two-Parallel Lambert projections, which is what many SPCS zones, including Texas, are based upon.
Lambert User Grid Projections
Again, seems like this would surely become the next hot app for cell phones, at least for our interests.
Kent, do any of the Delorme products do what we want?
dla
Lambert User Grid Projections
> Kent, do any of the Delorme products do what we want?
I don't know, but would like to find out. The utility of an inexpensive handheld GPS unit that operates in some meaningful rectangular coordinate system is huge. The Magellan's have a couple of annoying features, one of which is defaulting from Feet to Miles rounded to the nearest 0.01 for all navigation distances > 0.10 miles.
Lambert User Grid Projections
I have also found the “handheld” (resource/recreational grade) GPS units to be very useful for reconnaissance purposes recently. Getting to with a few meters of your “search position” without running a FORMAL Coordinate into the site is a real time saver (I drive, Spud runs the Garmin). When we get “close,” we bail out and hike to the search position.
I have approached it a little differently than Kent does (although the results are similar).
I simply wrote a small program (in BASIC) that takes my PROJECT COORDINATES (SPC, LDP, etc.) and generates the corresponding NAD83 XYZ values, transforms these to ITRF2000 XYZ via the 14 parameter transformation, and then computes the WGS84/ITRF2000 UTM Zone 'X' values thereof.
The input “heights” (elevations) can be VERY approximate without degrading the final solution in any practical sense, and EVERY handheld will handle UTM Coordinates without any user input.
Like Kent, I would like to see Magellan, Garmin, et. al., improve their support for “user defined coordinate systems,” but in the mean time, this works well for me.
Loyal
Geocaching
>I would like to see Magellan, Garmin, et. al., improve their support for “user defined coordinate systems,” but in the mean time, this works well for me.
The funny thing is that Magellan has brought a specialized handheld receiver to market that is configured for the geocachers. Apparently, the surveyor market is either too small, too segmented, or Magellan thinks we all should spend a few grand on Mobile Mapper instead.
Geocaching
"Apparently, the surveyor market is either too small, too segmented, or Magellan thinks we all should spend a few grand on Mobile Mapper instead."
I think that you have hit the nail on the head Kent.
Surveyors ARE a very small market, and handheld devices such as those we are discussing have only limited application in our work (albeit a very useful one at times).
I keep hearing rumors of TRUE sub-meter (autonomous) “el-cheapo” units on the horizon (still a few years off), and that will alter the paradigm significantly.
Just ANOTHER reason to keep ALL PROJECTS in georeferenced (NSRS compatible) coordinate projections.
Loyal
Geocaching
Loyal
Old buddie. They are already in our midst in the right hands and have been for several years.
Deral
:beer:
Geocaching
I take my SPCs in a CSV file and run them through Corpscon 6 set to print out degrees decimal.minutes.
Then when I want to navigate to a point I hand enter the LL using the height that's in there from the unit.
I don't usually bother to convert to ITRF especially when my coordinates are an educated guess.
Settings for Texas Coordinate System
BTW here are the settings for a 2-Parallel Lambert User Grid projection that, when chosen as the primary coordinate system, will display Texas Coordinate System of 1983 coordinates (in US Survey Feet), and allow entry of waypoints in those coordinates as well.
Settings for User Defined Coordinate System (2-Parallel Lambert Projection) in Magellan SportTrak and Meridian
Handheld GPS receivers to give State Plane Coordinates in US Survey Feet
Texas 4201
North Zone
NAD83, US Survey feet
Long of origin= -101.5
Lat of origin= 34
Std parallel1= 36.1833333333
Std parallel2= 34.65
SF= 1
Unit to meters= 0.30480061
False East at origin= 0656166.6667
False North at origin= 3280833.333
Texas 4202
North Central Zone
NAD83, US Survey feet
Long of origin= -98.5
Lat of origin= 31.6666666667
Std parallel1= 33.9666666667
Std parallel2= 32.1333333333
SF= 1
Unit to meters= 0.30480061
False East at origin= 1968500
False North at origin= 6561666.667
Texas 4203
Central Zone
NAD83, US Survey feet
Long of origin= -100.3333333333
Lat of origin= 29.6666666667
Std parallel1= 31.8833333333
Std parallel2= 30.1166666667
SF= 1
Unit to meters= 0.30480061
False East at origin= 2296583.333
False North at origin= 9842500
Texas 4204
South Central Zone
NAD83, US Survey feet
Long of origin= -99
Lat of origin= 27.8333333333
Std parallel1= 30.2833333333
Std parallel2= 28.3833333333
SF= 1
Unit to meters= 0.30480061
False East at origin= 01968500
False North at origin= 13123333.33
Texas 4205
South Zone
NAD83, US Survey feet
Long of origin= -98.5
SF= 1
Unit to meters= 0.30480061
Lat of origin= 25.6666666667
Std parallel1= 27.8333333333
Std parallel2= 26.1666666667
False East at origin= 984250
False North at origin= 16404166.67
Deralski
I must have missed that memo.
Which "sub-meter el-cheapo" units are you referring to?
Loyal
Advantages of Rectangular Coordinates
> Then when I want to navigate to a point I hand enter the LL using the height that's in there from the unit.
One advantage to working in rectangular coordinates is that you can take them directly from the handheld to do COGO and then input the results directly as waypoints for further seach. The initial search positions are fine, but as you start finding stuff, almost invariably new, refined search coordinates are needed.
Settings for Texas Coordinate System-Loyal
I suppose I should qualify that a bit. Maybe not recreational grade units but mapping units.
I've done submeter and sometimes centimeter level results with some pretty cheap units compared to survey grade stuff which comes at a much higher costs.
Correct for the 60 day, the offset from ITRF and NAD and you can get there in most cases with a unit under 2,000.
As long as you understand your tool and what it is showing you then it's not all that hard to make the shift to something worthwhile.
Deral
(Sharpening up the darts now)
Deralski
convert your spc to lat long and most smart phones do pretty scarily close. Or at least my T Mobile one does. I do not know about sub meter, but it has been running pretty close to meter level for me.
Deral
Okay...
A grand is a LOT cheaper than "survey grade," but hardly "el cheapo" to us CHEAPSKATES!
🙂
Loyal
