Hp41 Program question


I have a spiral program that has two codes to it that I don't know how to key in, and am not real sure what they are.

the codes are

1 E2



any ideas?


1 E2

Try [EEX] [2]


Try [RCL][YELLOW KEY][2][5]

Best regards.



1 E2: press 1, then the EEX key, then 2

RCL IND 25: press RCL , then the yellow shift key, then 25




Looks like your question got answered but:

Which spiral program is that? It's not Kirber's, or is it a modified version? I'm just curious because i used Kirber's years ago and did a lot of modifying myself. It was great as written but it did everything for everybody and at over 700 lines it was bulky enough for me to ask "what don't i need". I took out about 40 lines of program and 50 lines of subroutine that i didn't use and then put a few back in (A.K.A. peeing in it to improve the flavor). So DID someone write another spiral routine?

It's great to see someone using "aproriate technology". Theres too many surveyors now a days just getting everything loaded into a data collector by someone in the office and pushing the "next point" key.


Hi, D.B>;

I developed a lot of surveying programs for the HP41CV/CX at the time I was a student. I worked for a professional topographer and all programs he wanted I developed and listed. I have most of them still with me.

What I saw lately was non-topographers using very expensive GPS stations collecting data and sending these data on-line to their offices. They can do a complete survey in one day while it used to be necessary about a week to finish the same job. It's amazing in one side, but if you read again, you'll see the term "non-topographers" doing the job. The guys I saw only knew what was north, south, east and west. And their bank account number.

Too bad, too bad.

Luiz C. Vieira - Brazil


Hi Luiz,

If that is the way surveying is today, then I daresay the maps produced would very likely be garbage. GPS is really not very accurate--certainly not if you are surveying a building plot--it can be of 10's of feet! Unless of course one uses a "differential" GPS system, which uses a fixed ground station system to compare the gps signals, and then send adjustments via UHF radio----but is this being done in the case you are suggesting?

By the way,I will attempt further repairs to my 41CV--but I am going to try to test it one more time, first,--and then get the right glue.....


Bill Platt


Survey grade differential GPS equipment is easily capable of sub-centimeter accuracy, but even the cheap grade units can measure to within a meter and the really cheap handhelds can get to within 3 meters these days. RTK (real-time kinematic) units are very common with most surveyors today and the maps being made utilizing this technology are very accurate. However, vertical accuracy is only about +/- 2 centimeters with the more accurate units used by most surveyors, but this is usually close enough for most topography surveys, unless you are designing or redesigning a really flat parking lot or something similar.


So then this "survey grade" DGPS must be something entirely different from the USCG DGPS that was originally developed for use in harbor navigation (back when selective availability was active).

So, who is transmitting the DGPS differential signals? Are there permanent transmitters I was not aware of? Or is this a portable transmitter that the surveyor sets up somewhere?


DGPS is usually done with a permanent reciever or sometimes a temporary reciever. Either are set over a point whose coordinates are known more preciseley than is necessary for anything in the staking or topoing to be done. The data at the known station is recorded just like the mobile units and is compaired in the post processing (or in the rtk sometimes now-a-days). This gives to your new points a precision, and hopefully an accuracy, not much less than that known point carries.

USGS first order brass discs are commonly used for this and back in the 80's when the mobile units cost a quarter of a million gollies, Trimble had one running night and day on a known point on the roof at the plant near San Jose California, as a combination test, advertisment, and proof of its robustness. Since almost no one could afford two they also gave away the data to their customers for use in post processing. It wasn't too much help to folks over 60 miles away and way less over a hundred but the price was right. Any large metropolotin area has the same service for a fee and equipment is so cheap now that almost no one even rents.

Local positioning uses local transmitters and there is a mixture for things like GPS on a large subdivision. The recievers will pick up from satalites and a local transmitter. There will be a couple of guys running around using rtk units and putting wood wherever it is usefull.

There will always be the need for people to do things the old fashioned way. I hope. It is getting to be that even heavy equioment is mounted with GPS recievers but that application has a limited use so far. To make money moving dirt you care as much about how as where and GPS doesn't do how.

I'll stick to small jobs if i can and do it with real tools (like a 41) as long as i can. The pay is a little less but the work is more satisfying. It is also easier to work and get something done than to pretend with a bad terrain model and get blamed just because the computer jocky that made the mistake is in the office and made out of teflon. The saying "mistakes have been made, others will be blamed" comes to mind here.

Someone mentioned accuracy and had it right. Horizontally speaking; sub cm precision is common and sub cm accuracy is possible. As he said; the vertical is only about half that good so you have a spheroid (is that the shape?) about size of a pistachio and the truth is in there somewhere. (That was the single most funky description of residual i have ever heard.)

Anyway, Greg never answered my question: what spiral program is he using?


I have a friend who works for the state. All they use is GPS, and lasers. He has an old 41 with a survey module but doesn't use it anymore. He then transfers the data into a CAD program and then they use a plotter to draw maps of land plots.

No he won't part with the 41, I already asked.



Chris; That 41 shows people that he used to have to think for a living. It's image clairification.

One great thing about the hp survey pack; the vertical (parabolic) curve program is best stand alone vc routine there is. Many of the others could have been improved and the most important one on the rom is just badly written but that grades one is good to the last byte.


Well, that is interesting. I guess the techno revolution proceeds unstoppable.

My use and understanding of GPS comes from a different place---marine navigation--where centimeter accuracy was never an issue, but being off a hundred yards in fog on a narrow fairway is.

So, the USCG (Coast Guard) not the USGS (though maybe they were involved too?) essentially got in a quarrel with the Dept of Defense early on regarding the "selective availability" which rendered GPS considerably less accurate than LORAN C (using TD's) and in fact unacceptably so in the aforementioned situations. Even Lobstermen found early on that their LORAN sets were far superior for briging them back to their pots in thick fog.

But I have not been out navigating in over five years (amazing how time goes by) and so have lost track of what is going on. For instance, I am pretty sure SA is turned off now?

Another interesting isssue which came up in the early nineties when I was using GPS was that of DATUM discrepancies. It was not unusual to find that your GPS would on average put you, say, 100 yards to the east of the chart, for some place overseas. So,it turned out that you had to adjust the chart datum to match the datum of the satellite constellation.

Another interesting thing was that the whole system was in fact only experiemtal, and the satellites were in fact primary for other missions. If you listened to WWV broadcasts, you would hear, "users of GPS are warned that the system is not yet fully operational...". I know that the plan was to go into the next phase by putting up birds whose primary mission would be GPS. I wonder how that process is going?

And then there is GLONASS. Our Magnavox GPS receiver in 1993 was capable of operating with GLONASS, but we never tried it. GLONASS has a web-site, but I don't really know what the status is---I don't hear about it anymore.

-regards and thanks for your post!

Bill Platt


" . . . so you have a spheroid . . . about size of a pistachio and the truth is in there somewhere. (That was the single most funky description of residual i have ever heard.)"

I thought that was a description of my brain! (Except for the "truth" part . . . )


That phrase has got to be one of the world's great quotations. Is it yours, db?


....and the sad thing is; that's the best short one i could come up with. I guess i could have specified that the nut was in the vertical position.


Well, the context was certainly sufficient to suggest its orientation. But " . . . a spheroid the size of a pistachio, and the truth is in there somewhere . . . " Now that's one crystal clear turn of phrase! You're exhibiting a considerable gift for the translation of the abstract into the concrete. I applaud your effort!


GPS can also work in a mode called "carrier phase" where you are bacically figuting out how many wavelengths of signal you are from each satellite. At GPS freqs this is less than a foot per cycle. How fine you slice the final wavelength up can be fairly amazing. Long term moniroring can give you sub-millimeter accuracy over the width of the planet. You can watch continents drift in near real time.

You can also combine carrier phase operation with differential operation. A reference station is placed at a known location and a roving station takes readings relative to the reference. Real time kinematic measurments can be made to sub-centimeter accuracy.

And every 11 inches of GPS accuracy implies you have absolute time accuracy of 1 nanosecond.


Actually, carrier phase monitoring doesn't work too well on a planet-wide basis. The baselines are then becoming comparable to the orbit size of the GPS, and you have problems defining the phase center of the GPS antenna system. On baselines up to hundreds of km, you can get accuracies at the few mm level in a few hours of measurement. (The limiting factor on radio and laser geodesy is the Earth's atmosphere - the atmosphere is the equivalent of about two meters thick at radio wevelengths, and the effective path length gets longer at lower elevations, in proportion to both the atmospheric pressure (easy to measure) and the precipitable water vapor (MUCH harder to measure!)

I used to (and still do to a small extent) support a NASA project using very long baseline radio interferometry (VLBI) to do geodesy. On the longest baselines (intercontinental), VLBI is superior to GPS. On the shorter baselines, VLBI is marginally better than GPS, but about 2 or 3 orders of magnitude more expensive for the equipment (hydrogen maser time standards at $250,000 a pop and million-dollar radio telescopes)! So, GPS has just about taken over on the shorter baselines. However, GPS makes its measurements within the (rotating) reference frame of the satellites. VLBI uses quasars billions of light years away for position reference - a stable system at the 10e-10 radian level. So, VLBI is still the ultimate standard for the global reference frame. NASA also uses laser ranging to satellites for geodesy, with comparable precision to GPS and VLBI, but still with the problem of a rotating reference frame.

All three techniques are now used to measure plate tectonics, and with the longest runs of data (back to the late 70s), the formal errors on the plate rates are at the few hundredths of a mm per year. (Typical plate motions are a few cm per year - or about the rate at which your fingernails grow.)

If you have a two-way radio link, you can get the cm-level precision of base-station GPS back into the field. You can plow a field or move the dirt to make a level parking lot with a real-time GPS unit in your (Caterpillar) tractor.


That was fascinating Dave, both in content and the way you explained it. So much so that i saved it to read again.

Yes you can do most anything you might want to do in earthmoving using gps but: 1)the cost of making a terrain model still makes a cutoff point where many jobs are too small or too busy to warrent it. 2)The software knows to say raise or lower the tool on your cat but it doesn't know which way it wants to push the material or what to do with varying types(soil/mud/rock). It will eventually. Just as 95% of the art and science has gone out of "the art and science" of surveying, due to overcomputerization, i'm sure that someday all the thinking will go out of sculpting the earth.

I am also sure that automation will not get it done better or faster than experienced people could do it with the eye and hand and brain. Let me use surveyors as an example again because they are 10 or so years ahead in using the same technology. All that the field computers and data collectors which you see surveyors with now days have done is make it so people that can't do math can be surveyors. It is that way it is too much of the time now, both in my union and the non-union area. At least my union still gives classes in math, some of the old methods, and the theory behind what we are doing.

Please let me give one more observation. When i started surveying in 81 there would be a three man crew; one man calcing, one shooting and one pounding wood. Depending on variables like the correctness of the topo & plan and the number of gun setups plus the amount of control that needed to be done a good crew on a good day could get from 70 to 125 points in the ground. Now a two man crew, a gunner and a chainman, go out with a data collector full of coordinates that it took an office worker most of the day before to generate and check and on a good day they get between 70 and 125 points in the ground.....Unless something goes wrong with all the computer equipment or unless the office calculations got rotated or something. Then sometimes nothing gets done because all too often the people in the field are just what the employer was looking for: button pushers.

I am not a technophobe. I am just sick of technology for the sake of technology. I do think that one person gps surveying is the wave of the future. To tie this all into the forum......too bad that the new hp won't be doing any of this, isn't it?


HP "was" surveying in the 70s when I started. The HP3800 distance meter, then the HP3805 for longer range, then the HP3810A was the first "total station" that measured distances and angles accurately in one instrument. The HP3820 was the last of a great era of HP surveying instruments that I had the pleasure of using in the field. All the while, they were making great computers and calculators for surveyors and engineers like the HP-41 that I carried every day in the field and still have one on my desk as I write. Even used the 41s, 71s and 48s as data collectors with total station instruments at one time or another. But that was then and this is now and it is really is too bad that the "new" HP won't be doing any of this in the future. Thanks to those that explained GPS surveying better than I ever could have done.


There are still a few die hard old timers out there. A local surveyor had his HP41CX with Sup-R-Rom stolen from his truck. It was like his dog died. It took me around a year to find him a new Sup-R-Rom... which he keeps under lock and key.


I still have a Sup-r-Rom and a somewhat rare Tom's Rom for surveying along with their original manuals.


Yes, I also have a TOMS ROM, but it has the name of a different company that had licensed it... I don't remember the name right now.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP Prime: run a program in another program Davi Ribeiro de Oliveira 6 606 11-11-2013, 08:28 PM
Last Post: Davi Ribeiro de Oliveira
  [hp41] reading the catalog under program control Wolfgang 3 402 02-25-2013, 01:32 PM
Last Post: Dan Grelinger
  HP41 Blank formulars for program documentation? Wolfgang 3 366 02-15-2013, 11:08 PM
Last Post: Wolfgang
  42s program question David Persinger (US) 5 410 08-09-2012, 06:34 AM
Last Post: David Persinger (US)
  WP34S program question Mike Maiorana 12 731 04-05-2012, 03:09 AM
Last Post: Steve Simpkin
  HP41 navigation module question Muhammad Ahmad 19 1,111 07-12-2008, 04:49 PM
Last Post: Dan Grelinger
  HP-41 MCODE: Making an MCODE program call another MCODE program Geir Isene 10 760 01-13-2008, 05:58 AM
Last Post: Raymond Del Tondo
  HP41 Question Vincze 2 265 08-10-2007, 07:43 PM
Last Post: Dave Colver
  Program question Vincze 19 1,128 08-02-2007, 09:27 AM
Last Post: Thomas Klemm
  15C program question John Nelson 7 531 06-06-2007, 10:01 PM
Last Post: Karl Schneider

Forum Jump: