I couln't understand all the hoopla over a handheld GPS(esp. for the price).

Of course I've only ever used GPS for surveying.

ANYWAY, am I right to assume that virtualy everyone that has a MobileMapper, got it to do GIS work?

I would like to find a "junior" mobile mapper(?). A GPS usint that is setup to accept coordinates from an ascii file in P,N,E,Z format.

Now, I know there are a lot of ways to get Lat & Lon into a GPS, but I don't have a program(Cad) that works in or readily converts to Lat/Lon and although I do have a program that will convert a batch file of SPC data into DDD mm ss.sss(CorpsCon), the final data is not usable(because of the spaces).

In fact, a transfer of a DXF file(which I guess the MM does), would be exactly what I could make most use of.

Are there any other GPS units that will accept a DXF file, or a direct transfer of SPC's in P,N,E,Z?

I feel your pain. Gis makes its own work!!

Posted By Douty Steven on 5/8/2004 at 11:00 AM
I own several (6) ProMark2 units and don’t think it is possible to say enough good about them and the support staff and software. Based on my ProMark2 experience I bought a post-process capable MobileMapper last week.

I have only been using the MobileMapper for a little over a week so ANY PROBLEMS THAT I AM REPORTING MAY BE DUE TO USER ERROR NOT SYSTEM ISSUES.

I ran a science project in my yard that gave me results that appeared to confirm the claims of the manufacturer. This project included a few points under trees and was post-processed using a ProMark2 as a base located within 100 feet of the rovers.

At this point I thought I had died and gone to heaven!

I then took my MobileMapper and two ProMark2 units to the field to map wetlands. The area to be mapped is in on the eastern slopes of the Blue Ridge Mountains and in deep woods. I set my ProMark2 units as base units within one half mile of the project in open sky country and mapped wetland flags and previously located points for three days.

As a check on the quality of the data I occupied several points more than once and for varying lengths of time.

CONCLUSIONS: (BASED ON LIMITED EXPERIENCE)

1. With wide open sky the MobileMapper yields answers as advertised.

2. I can’t find that the length of observation time has much impact on the quality of the position. I have occupied the same point for thirty seconds, immediately re-observe the point for 1 Min., then for 2 Min., 5 Min. and 20 Min. The coordinates produced are in agreement with one another well within speck. I am assuming this is because of SV geometry.

3. When I return to data points hours (days) later and re-observe (heavy woods) I will get post-processed coordinates as much as twenty feet different from the original position. Good PDOP and 6+ SV’s.

4. I can’t find any information in the output data that indicates the dependability of the answer (does not appear to be a function of PDOP or number of SV or length of observation).

5. Elevation appears to be very difficult to reproduce.

6. I can’t find a way to compare coordinates of points that are close together on the MobibleMapper Office screen. The graphics will not allow a tight enough Zoom. I can export and compare with other software.

Good luck. I would love to see follow up from others on this thread.

Douty

1.Yes, same as my conclusions. Very solid and repeatable results

2.Again, yes in the post-processed files, but time is very important if you are going to use WAAS only. Not only the time on the point, but the amount of time the unit has been running before logging on a point.

3.I can't address this issue since we don't have heavy woods in Oklahoma, nor would I expect a 40K unit to produce any better results than the Mobile Mapper in harsh canopy.

4.I disagree. I do find the dependability of the answer is in the PDOP's and number of SV's.
This would not apply to points taken in harsh canopy. Multipath cannot be removed by code or carrier processing.

5.I also disagree. I find easily repeatable and dependable elevations from our Mobile Mapper in the post-processed data.
Again, all bets off in the heavy woods.

6. You can occupy a point then move the cursor to the other point and get a azimuth/distance. Of course, the screen zoom only goes down so far, and does not allow you to easily check points that are within a foot or so, but then the equipment is not that accurate in autonomous so I'm not sure it would be much help anyway.

I have put in our control points and such as waypoints. Then you can get exact bearing/distance to this point from where ever you currently are located.

JD and I did this when we were testing the WAAS corrections and his real time corrections with the Mobile Mapper this summer.

John.

The hoopla was about the size, weight, power and cost of the new Mobile Mapper. Our PROXRS weight 15 or so pounds and is bulky. The MM does what it does and fits in my shirt pocket.

The ability to take maps to the field, such as DXF or Shape is a huge help when 'surveying'.

It packs a huge wallop for the relative cheap costs involved.

I know of no 'junior' receiver of any brand that fits into the same price or performance.

You have either recreational grade receivers (Meridian, ect) or Mapping Grade (MM, GeoXT,PROXRS and many others).

I have a mile of new waterline on a very busy 4 lane road. The survey was done some months ago and these projects take along time to bid and actually begin construction. I uploaded the entire project (all the topo and boundary work) and could walk that mile in under a couple of hours to find the few changes (such as a new telephone pedestal) that might impact construction. Not sure if this falls into GIS or Surveying.

Deral

Deral,

Thanks for the response.

It is starting to look like the only solution that works in harsh canopy is L1 with redundent and long occupations.

Once again; With wide open sky the Mobile Mapper yields post processed answers as adverized. In heavy canopy we are on our owne.

Steve

John,

Read my new reply below on AS2.7.

I still don't think you need a new receiver to get your SPC into a handheld GPS receiver. I'm able to import our AutoCAD points into either our Garmin eTrex or PM2 with ease. If you need additional help in doing it, then shoot me an email.

Tommy McClain

I have yet to see anyone post a spreadsheet for long L1 repeatable baselines that in heavy canopy is reliable.

I here from all the boards that many think if you log for a very long session, even in dense forest you can get a solid repeatable position.

I would love to see some results if anyone has any where they have done muliple sessions or checked into points with the TS after a long session.

And Douty..I'm still learning the limitations of the Mobile Mapper, but thus far I've found more extra gems than gotcha's.

Deral

I have been testing a Mobile Mapper as a possible replacement for aging (and heavy) Trimble Pro-XR units. So far I have found similar results to what others have reported here - the MM works great in the open but under canopy the results are less predictable. (just for the record - the canopy I generally work under is fairly extreme - Pacific Northwest old-growth forest).

The one shortcoming of the MM that I see is the inability to record/output a measure of the error for a point feature. With the Trimble units (and Pathfinder Office) one could output a standard deviation for each point, similar to what one can do in Solutions with the SE or 95% error display.

Alternatively (again using the Trimble hardware/software) one could output all the raw positions averaged on a point to look at the spread of those positions and do one's own calculation of error ellipses.

Has anyone using the MM with MobleMapper Office found a way to accomplish this?

Roger

The lack of tools to verify a post processed position is a concern with the mobile mapper software. Most of us want to push a gps unit so that is collecting data under less than ideal conditions. I need some tools to indicate if the resulting data should be saved or abandoned.

By a combination of occupation time and post processing and then looking at a plot of your 1 or 2 second code based track data you might be able to get an idea of how good your ultimate X-Y position was. I think you can set the mobile mapper to track and then view a plot of your track data over your position points.

Submeter X-Y is fairly easy out in the open. I suppose high accuracy repeatable X-Y under canopy or obstructions is the holy grail. I like gps mapping this time of year because most the leaves have fallen, but I guess it's no big help in the tall firs and spruce.

I’ve become accustomed to the power of the Promark and Ashtech Solutions system where you can get a real elevation along with a solid x-y if you do things properly. Even if the elevation is suspect you start to get some comfort with Promark X-Y results using repeatability and partial solutions.

I want software that dumps my processed and adjusted gps data into a real mapping package as soon as I can. I see advantages of being able to bring lots of data along with you if you can easily find it out in the field. The integration of the Mobile Mapper CE , Ashtech Solutions and Arcpad is what really interests me.

Based on questions from users and my own science projects I submitted a feature request for improved QA/QC tools for MobileMapper Office.

However, it is a serious mistake to conclude that statistical analysis is a guarantee of accuracy.

There are still three words that guarantee accuracy with any type of measurement. Redundancy. Redundancy. Redundancy.

I'm also anxious to use the MobileMapper CE but the MobileMapper steps me very quickly from field work to data for my CAD, COGO, and GIS software.

The mapper sounds neat and I want one. I just need to find out a use for it! It really looks neat. If more accurate than my gps handhelds Im sure Id like to use it for something.

Roger..

The ability to output RMS, standard deviations and such was the first thing I sent to Phil after using the MM for a week.

I think we have both graduated from the same school.

Those that have never used any GIS grade equipment (such as the PROXRS) units don't see anything missing in the software. Those, like us, or surveyors who have done static work, want a bit more analysis of our data and some quality checks.

Pardon the comparisons , but it it necessary to the explanation.

I do alot of GIS related work, and many times I have gone back to reshoot something based on the statistics of the data after post-processing. In the field I had plenty of birds, good DOP's but the point just didn't process with the stats I like to see. The times this has happened are very statistically small, but it does happen. Maybe it means the point is 5' and not submeter, but the surveyor in me wants it as close as the equipment will allow.

With the MM, then I have little in the way of other verification. I'm a surveyor who has GPS since day one, so I think that I 'feel' when I should do an offset or something because of a location.
I check the DOP (preplanning) for the day and I look at the space weather.

Not something that many 'just' GIS gathering folks would do. I treat my sub-meter work the same as my survey grade work. Good procedures and technique produce good positions. Maybe I should develop an online training course for the MM for non surveyors. Might be a good retirement job!

I think Thales marketing looked more at the 'GIS only' folks and sorta overlooked us that understand the concepts on a different level. I'm sure they will address this in a future MM release. (please..please...)
Thales, my opinion, is marketing and treating the MM more as a 'steroid version of the Meridian' than the true survey instrument that it actually is.
They will get it right.It's a great tool.

And to answer your question. No, I have found no way to do any checks in MM office at this time.

L.A.
I use Ashtech Evaluate often when working with new units. Great little tool that's free, but it really doesn't help with post-processed interpretations. The MM compared pretty favorably to our aging ProXRS in unprocessed data just looking at the scatter charts. I wondered how much difference I might see in the larger Trimble antenna versus the micro antenna in the MM. Thankfully, it appears the newer MM was every bit as good as the older Proxrs antenna. This surprised me a bit, but after all the ProXrs design is a few years old.

Again,We surveyors are trained to use a careful eye on our data and results. MM Office doesn't allow much eye contact with the data as far as how things are working.

And finally for my buddy Phil.
I do agree that statistical analysis does not guarantee accuracy. However, with GIS work there is no redundancy. You shoot a fire hydrant and go on down the road. It's a side shot from some base and nothing more. Having some tools to evaluate the post processed point is something that would at least help us evaluate the results.

Surveyors always have a critical eye on 'the computer output the results' type of answers. We like to dig a bit deeper.

I think maybe adding tools, such as editing raw data and such are not needed. Just more statistical interpretation of the data that we already have.

I would imagine much of this is already calculated and just needs to be output in the reports.

And finally, finally,...For Sam Mets.
Find a small town or towns around where you work. Talk to them about updating their infrastucture maps. Maybe not even supplying digital maps, but just better atlas (hard copy maps). Most small towns are lucky to have a copy machine and rarely have AutoCAD/ArcView..

One job will put a MM in your bag of tools and money in the bank.

Search on 'Mobile Mapper' , this board for several p