Product Review: Thales ProMark3

A 1.155Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE

The ProMark3s have been out for a while and in addition to the great static and kinematic surveying functions that were available in the ProMark2 they include tools that will help you expand your surveying business. They will allow you to collect and provide GIS data at a faster rate than by conventional techniques alone, and you can still do control for regular land surveying projects as well as GIS projects.

While "GIS" is not part of the vocabulary of all surveyors, it is something that we have been doing throughout history. We just called it mapping. Every plat, plot, or map is essentially a miniature GIS. The bottom line is simple: if the land surveyor does not supply the GIS data then someone else will! Who better to explain positional tolerances than the surveyor?

The ProMark3s have handy "do it all" tools for most of your usual projects as well as for your expansion into GIS data collection. Sure, you can do that with dual-frequency units, too, just not as easily or inexpensively as you can with the ProMarks3s. The ProMark3s come with Thales GNSS Solutions and MobileMapper Office software, plus two units and a dandy Getting Started Guide," which for those of us "avoid the manual at all costs" folks is almost like having the sales rep with you.

ProMark3s come in a well-padded blue Cordura case, and contain all the equipment you will need to get up and running (Figure 1). When I could not find a likely port in which to plug in the charger, I turned to page 3 of the hard copy of the Getting Started Guide (I printed out the guide because I get along better with printed manuals than digital ones) and solved my dilemma. I opened the battery cover using my car key in the Zus fastener, twisted about a quarter turn, and inserted the battery. I replaced the battery cover and mentally thanked the person in the Thales organization for using those simple, quick, and positive fasteners. Initially, I wondered what that device with all the ports was for. It turned out to be the I/O module. I attached it to the back of the unit and plugged in the battery chargers and then the charger cable (Figure 2). This set them both to charging for the initial six-hour period. Figure 3 shows the front of the unit.

The next day I began to get acquainted with the ports just by poking around to find out what the icons represented. It was fun and I never did "lock up" the firmware. I loaded the GNSS software and the USB driver and discovered that I did not have a USB cable with the proper end. The I/O module has a serial connection, battery charger coaxial port, and two physically different USB ports. All my USB cables had one end with a printer type USB connection. I purchased the proper cable and now I can connect to both kinds of USB ports. Next, I installed the MobileMapper Office software. Both the GNSS and the MMO software installed without incident. Then I downloaded the guides and manuals and printed the Guide and the Mobile Mapper Office Software.

Since I had already written an article on the ProMark2 some time ago using the static mode for control surveying, I was eager to give the GIS setup a try. You have two choices with the ProMark3 when collecting in the GIS mode. One is to use the ProMark3 alone with its internal antenna, which is certainly the least cumbersome and fastest. There are no cables or prism pole to plumb, but you have more tolerance on the positions collected. The other choice is to use a prism pole Figure 3 and external antenna that connects to a coaxial port on the left side of the Promark3 (sealed by a flexible rubber flap), which is in turn attached to the body with a screw (one of those details that proves Thales is listening to users and committed to robust equipment that can be used in all types of weather).

I attached the hand strap with the I/O module on, but decided instead to just use the internal antenna, so I removed the I/O module. My first attempt with no consultation of the guide was not too good. So, out came the guide and I proceeded (mostly following the directions) to do my first GIS data collection sets first to locate some utility poles, and next to do a line feature. It took less than 10 minutes to locate the poles and less than 10 minutes to walk around half the block where I live to pick up the middle of the alley and surrounding sidewalks. Try to match that time with conventional equipment! You can see the results (Figure 4) on the accompanying graphic, my mistakes and all. The "unknowns" were my mistakes with the stylus while walking. If I am just looking for the road or the poles to perform maintenance, why do they have to be located within 0.01 of a foot? They simply do not have to be that close. If I were doing photo control work using the pole for a photo ID point, then yes, or design for a building, then yes. But for maintenance I just need to be in the block and then get to the proper pole.

My line started in the middle of the northwesterly line and I walked at a steady pace to the sidewalk using the default five-second recording interval.

Pausing at the corner caused the unknown when I switched to a two-second interval. Next, I continued around the sidewalks. Notice the space between the blocks, representing data positions on the northeasterly leg. These spaces were caused by being three feet from the walls of the one-and-a-half story former Alltel building (Figure 5). There was not much southern sky for the satellites. Figure 6 shows the conditions along the sidewalks.

You can readily see this when you are collecting the data. The screen shows the number of satellites and the PDOP values as well. In some cases, during this data set collection, the numbers were replaced with dashes indicating the absence of reception of signals of any SVs. Hence, no positions were calculated since there was nothing to be solved for and no SV numbers or PDOP numbers were reported, just the dashes. This is not the fault of the equipment, but of me, the operator of the equipment. If I were collecting this for a GIS client and not a magazine article, I would have to evaluate the positional tolerances and supplement the spaces with longer occupation times under different satellite geometry, or use a total station if I did not achieve the required positional tolerances. This comes under the heading of "professional judgement," one facet of which is to use the proper equipment to achieve the positional tolerances required.

With a linear regression, or "best fit line" performed on the data presently collected, my opinion is that even with the "spaces" the best fit line would be absolutely acceptable. Actually, by deliberately collecting the data under extremely poor conditions for any GPS equipment, the results were far superior to what I anticipated they would be. I wheeled 280 feet on the northeasterly leg and 280 feet is what I measured with the Mobile Mapper software measuring tool. My biggest difference between the wheeled measurements and the software measurements was almost two feet and that was on the southwesterly leg with the poorest southern sky visibility, which is exactly what I would expect. I was amazed and very pleased to know that this type of consistency could be achieved under these field conditions. This was the best performance I have seen for any GPS equipment used in this type of field environment. (This would be Step One if you were evaluating your own equipment under varying conditions to understand what you and your equipment are capable of under a wide variety of data collection scenarios and situations.) And this was done with the internal antenna when there were no WAAS signals in my location due to the WAAS SV being moved to a new position. The algorithms for multipath mitigation and loss of lock have been improved by orders of magnitude in the ProMark3 firmware. Yes, the ProMark3s are SBAS capable and I can only contemplate how the spaces would have been reduced and the tolerances would have been tightened if WAAS had been available.

Mobile Mapper Office comes with a feature editor library. I used the tutorial library for this article, and you can customize your own for the particular job you are doing. You can even set up several for most anything you can contemplate. You can also import and export way points and import background maps.

The one facet that I did not try was GIS post-processing. To really get to know all the in and outs and capabilities of the GIS software and the ProMark3s would take a couple of months full time, and two separate articles.

Now, on to the static survey session. If you are a first time user of static GPS for surveying, I suggest you download the GPS information on the Internet from the Thales FTP site. It has the clearest and most understandable explanations of network design in a very concise format.

I set up on the east bank of the Allegheny River and in my back yard (Figure 7). Following the guide once more, I powered up and began collecting data. When the "log" button is pressed it brings up a screen where you can enter your site ID, Survey Mode, site description, antenna height, Units, Height Type, and recording interval. Tap the "log" icon and the Data Collection screen comes up. Here you are presented with your site IS, file name, observation range, elapsed time of observation, numbers of satellites being tracked, PDOP number, a power remaining icon, free memory icon and the "done" icon to tap when you end your session.

The back yard set up was not the ideal place from which to perform static observations, but I gave it a try anyhow. You can see the prism pole clamp/ProMark3 holder in Figure 8. As can also be seen in Figure 8, the antenna plugs into the side of the unit. Experience has taught me to make longer observation times under these conditions, which I did. I was expecting to see fewer satellites in the back yard than on the unit on the river bank. Imagine my genuine surprise when the number of satellites was usually the same at both locations. Most of the time I was monitoring 7 or 8 SVs with PDOPs around 2.0 for the two hours I observed.

For security reasons I took advantage of that fact, and after thirty minutes I powered down the unit by the river bank and moved it to another point in the yard. These points were set up for one purpose and with only a total station in mind, certainly not for GPS observations. They are where I perform my pointing tests on the total stations that I review. Not a good spot at all, less than three feet off a 43-inch DBH silver maple. So, set it up there is just what I did.

I powered up the unit and began logging data. I let it run for an hour and a half, not really expecting much useful data at all, yet I was tracking and logging data from 7 to 8 SVs every time I checked and had PDOPs around the 2.0 give or take a tenth or two. Again I was seeing similar data information on both units. I suspected that I might get some kind of results considering what these 3s did with the internal antenna, but little did I imagine what I was seeing on the data collection screen.

Rather than shut it down after a few minutes after the start of logging and going to a more clear, better GPS site, as I had originally planned, I just let it run. I can tell you it was worth it! Rather than shut it down after a half hour, I continued to collect data until the other unit ran out of memory and then shut them both down. I never bothered to clear any memory from either unit since they were shipped to me and the one with the 32 MB card still had about 90 percent of its memory left after all the GIS collection and a couple of hours of a static session. The unit I used for GIS collection still had about 75 percent of its battery left, too. In fact, the only charge the batteries had was the initial charge when I first got them.

Granted, I made a lot of poor decisions (poor sky visibility, not clearing the memory, not having fully charged spare batteries, and not having two-meter fixed-height poles). Still, the units performed flawlessly even with my input mistakes. What I did with these units speaks volumes of how these robust units perform and gave me great confidence in the results that I would expect when I used them in good GPS setting. It proved I could still rely on them for the occasional poor GPS site. Current users are reporting that they are achieving solid results with less than half the session times usually recommended for L1 units.

I opened the GNSS Solutions software, set up a new file and attached the I/O module to the back of each unit. The download went flawlessly and I was ready to blunder detect my data. No blunders, always a good sign for the rest of the processing. Impatient for the results, I chose to process, solve the vectors, (only two in my case), and adjust the observations in one step. Normally I would solve for the vectors and then look to clean up my data set.

This I why I was so happy with the tracking of 7 to 9 SVs. You can look at at each SV for loss of lock, cycle slips, and block one or two of the SVs from your data set and then reprocess the remaining data. In my case I could drop even 3 SVs. For this article I did not do that. I just processed the data and compared the vector between my backyard points to the actual measured distance. The conventionally-measured distance is 58.286 feet, the result of numerous EDM shots and some ordinary taping distances. So what was my GPS vector between those point at grade? According to the report, my processed vector length was 58.291 feet. I was really expecting two or three tenths of a foot at best.

I would like to do a follow up article on the ProMark3s and the GNSS Solutions software in a future article. I would like to do a network with some NGS markers, some stop and go and some kinematic, as well as delve more deeply into the GNSS software and processing the data. Perhaps a follow-up article could be timed to the debut of NGS’s online OPUS L1 only service. I checked with NGS before I wrote this article and it is about a year away.

In conclusion, the ProMark3s are rugged, reliable and able to perform under very adverse conditions. Check out other opinions on the online surveyors’ sites, or when you are at your next society meeting or yearly conference. Arrange a demo for yourself. Thales was the first manufacturer to risk an out-of-house presence on a surveyors’ site where practicing surveyors could comment. Some surveyors have purchased Thales equipment because of that presence. From what I see in their hardware, firmware, and software, and most importantly in their customer support, it is very evident that Thales is attuned to feedback from the surveying community. The ProMark3s are another firm step in the tradition started by the Locus and the ProMark2s.

Al Pepling works forMonaloh Basin Engineersin Pittsburgh. He is licensed as a professional land surveyor in Pennsylvania, as a professional planner in New Jersey, and is a past president of the New Jersey Society of Professional Land Surveyors (NJSPLS).

A 1.155Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE