Monthly Archives: August 2013

New Firmware for PM800 and PF800

ProMark 800 and ProFlex 800

New firmware has been released for the ProMark 800 and the ProFlex 800 receivers.

[ ProMark 800 ] [ ProFlex 800 ]


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Low Distortion Projections: Mania, Hype or a Great Thing? JDtM!

Prerequisite Reading: If you don’t get LDP, read [ THIS ] first.

Shawn Billing’s excellent article in American Surveyor on ‘Low Distortion Projections.’ See [ Ground versus Grid: Low Distortion Projections—Part 1 ] is out.

I count Loyal Olsen to be a good friend (and drinking buddy.) Loyal is the king of LDP’s. I promise you, he is the king.

I have made a couple of Scale Factor Specific YouTube videos on [ Scale Factor ] to help customers figure out why they can’t match a total station shot to a GPS inverse.

Yesterday I met Michael Dennis in person! (You remember he knocked it out of the park on [ Nightmare on GIS Street ], right?) He showed me a crazy great [ web app ] that produces LDP’s using visual methods. Way cool. (Actually more than way cool. Awesome? Yes!)

Most everywhere I go, I hear about LDP’s. They are the new rage.

In most circumstances you can design a LDP (or better yet use the web app above) that is good to 10-ppm over a township sized survey. But not always. Sometimes they still blow up. Sometimes the job is big (think pipeline, transmission line.) Sometimes there is a couple thousand feet of relief in a mile. But, in most circumstances LDP’s are just fine.

But I am a contrarian. I don’t like LDP’s. Here is why:

1. State Plane was first pass at simplifying the round world into flat space coordinates. Our ability to survey accurately over long distances was not much better than the distortion and we accepted grid coordinates for the simplicity of being able to use an X,Y,Z(Height) coordinate system that could be easily inversed in the field.

2. At higher elevations (like where I live/work) we need to introduce a scale factor so that inversed distances from coordinates exactly match measurements at ground. For small jobs, we can pick a single scale factor, accept the small resulting errors and get our work done.

3. It was not a big deal when we were pulling tape (chain) and turning angles with transits, but golly it does not add up so well in these days of 1-second total stations and GNSS driven GPS receivers. On big jobs, state plane grids with a single scale factor to ground rarely work out well anymore.

4. LDP’s are the next step in working a bit better (I did not say smarter.) The convergence angle is smaller over a job (but it is not zero everywhere and can not be ignored.) Its better, but it still…sucks. Just in smaller breaths.

I can’t wait until we have 4,000,000 overlapping LDP’s in a variety of projection types, all with different datum and reference elevations. ESRI will be able to distribute 4,000,000 PRJ files with ArcAnything! That will certainly make the world a better place. Surveyors can use custom projections for jobs and not release the projection information. Thereby insuring a decent retirement.

6. Soon LDP’s won’t be good enough and we will design 100 micro-LDP’s (call them uLDP) for a single job. They will be piecewise linear and we can spline-fit the intersections. (I tell you this is really going to be great and simple!)

The world is NOT flat. We need to stop trying to make the world flat. We should accept it for what it is: a complicated oblate-ellipsoid like blob (think squashed basketball.)

So what is the solution? Use double-precision numbers, survey with any underlying projection (pick geographic or XYZ Cartesian for all I care) and ‘Just Do the Math.’

More on this JDtM stuff later…


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OPUS Projects: Training

I am two days into the four day NGS ‘OPUS Projects’ training being held in at the Corbin VA observatory. Wow, this is cool.

Located next to Fort AP Hill the Corbin Training center which also houses the Fredericksburg Magnetic Observatory.

The NGS Antenna calibration piers are out back:


ImageThats the robotic absolute calibration fixture on the right in the foreground.

Anyway, back to ‘NGS OPUS Projects.’ OP is going to change the way we all do control going forward. It will take me awhile to digest everything but here are some high points:

o OP has been around for a 1/2 decade

o OP is a piece of cake to submit observation files to using the existing OPUS web submission page. (You can have your crews submit files directly from the field.)

o OP allows you to delegate functions: crews can submit and attribute shots; sessions can be administered by a project leader and the final adjustment can be performed by the manager.

o OP will magically fix observations. I have test files that only use 80% of the observations and have 60% fixed observations when processed in OPUS. Running the same files in OP, with other nearby observations results in 98% used and 90% fixed. Magic.

o OP takes care of all the framing issues. Everything is processed internally in IGS08 (or whatever the latest frame might be.) Then OP converts to NAD83-2011.

o OP is easy to use. Really easy to use.

o OP is free.

o I trust OP. Today I ran a fairly large job that encompassed 3-days, 24-hour observations for 5 south western utah TURN stations. I processed against 8 CORS sites. Results look excellent. Then I unconstrained all but one of the CORS sites and everything still fell into place (within +/- 1 cm.)

o OP does all of the dirty work for Bluebooking (that’s tomorrow!)

o OP generates some killer reports.

o OP is going to come out of beta in September (maybe, probably.)

In any case, you’re going to hear a lot about OPUS Projects over the next year. It is the real deal and it (if you doing work with accurate positions) it is going to change the way you do things. OP is going to save you time. OP is going to produce a better work product. In short, I think that OP is going to significantly change geodetics in the United States. And since it works anywhere, I suppose the world.




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