Using GPS to lay out a field

[quicksandfarmer]

I clicked on the link to look at a pic of the equipment. It looks like it is just the guts of a GPS receiver. I saw where you mentioned putting a metal tray under them for reflections, which is called multi path. Surveying equipment has that stuff built into the housings and the software also helps in rejecting multi path.

Does your equipment just track American satellites? I am not sure how many are floating around up there now. Gps(USA), European (galelio), Japanese, Chinese (Bediou sp?) and Russian (Glonass). I first started using GPS about 1993 and at that time there were long periods of the day you could not work because there were not enough satellites. With RTK you need 5 to get a fixed solution and 4 to maintain it, that assumes no obstructions. These days it not uncommon to track 15 to 20 satellites.

Do you have this in some kind of housing? Are you using some kind of pole? Kudos to you to get it working, that is way beyond me.

The kit is just a circuit board although it comes with a GPS antenna and a radio antenna. It looks like this:

This is the housing I'm using:

Small Plastic Project Enclosure - Weatherproof with Clear Top ID: 93 - $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits

I drilled holes in it for the antennas and the USB cable.

 

[bdog]

This is very innovative. The limitations of your paint wand are impacting your accuracy much more than the limitations of your GPS. I would look into buying what is called a rover rod. It is a collapsible pole that is 2 meters tall. You mount your receiver on the top of it, it has a bubble level mounted on the side of the pole so that you can tell it is plumb, and it goes down to a point on the bottom. Using one of these I have done some very precise things such as embedding anchor bolts into concrete slabs as they were poured that later the columns for the building were bolted to. Not much room for error there.

 

[quicksandfarmer]

I tell you that痴 a heck of a setup. I assume the black box in the center is the GPS antenna? One thing that will help is to get that setup in the air. We usually use a 2 meter pole to get it up over our heads and the base sets on a tripod about 5.5 feet high.

Thanks. I think I could mount it on a camera tripod pretty easily. It's good to hear how it's "really" done, I started this not knowing anything about GPS.

 

[dodge man]

The way we do it is with something called a Tribrach. It mounts to a tripod, one that is a lot heavier than one for a camera. The tribrach contains an optical plummet and a level bubble. The optical plummet is just a fancy plumb bob that uses optics instead. The tribrach lets you screw it to the tripod and be over a point and level. The GPS antenna usually has a set of threads that let you attach it to the tribrach.

This setup lets you setup over a point in an exact manner, which is sometimes a known monument or a new point. For new points they can often just be a random place that is easy to get to, we often use large nails or rebars. The idea is to always use the same point as your base so the coordinates are consistent. The threads on this stuff, the tribrach and GPS pole are just standard plumbers pipe threads I think.

Pretty ambitious to build your own GPS system and it looks like you pulled it off.

 

[dodge man]

The attached photo is our old GPS system a Topcon being run by one of my coworker. On top of the pole is the GPS antenna, it also contains the radio and the chips and board. Half way down is the data collector. We also have a 35 watt radio that we can setup with the base that gives us a radio range of over 10 miles or we can use the built in radios which have a range of over a mile.

Our new system, a Trimble has all of that plus a VRS system. With this we can use a hotspot to link up to the internet and use multiple bases tied into the system. Some states offer this service for free, in Illinois we have to pay for it, $2500 a years as I recall. With VRS you don’t need a base.

One thing about your system is it must have RTK software built in, called an RTK engine. It’s not just the hardware that makes this all happen but the software is an even bigger part of it.

 

[quicksandfarmer]

View attachment 652700

The attached photo is our old GPS system a Topcon being run by one of my coworker. On top of the pole is the GPS antenna, it also contains the radio and the chips and board. Half way down is the data collector. We also have a 35 watt radio that we can setup with the base that gives us a radio range of over 10 miles or we can use the built in radios which have a range of over a mile.

Our new system, a Trimble has all of that plus a VRS system. With this we can use a hotspot to link up to the internet and use multiple bases tied into the system. Some states offer this service for free, in Illinois we have to pay for it, $2500 a years as I recall. With VRS you don’t need a base.

One thing about your system is it must have RTK software built in, called an RTK engine. It’s not just the hardware that makes this all happen but the software is an even bigger part of it.

Of all the places he had to pick that exact spot to take a reading?

 

[dodge man]

That’s home plate on a baseball field. It’s a good example of when the model for machine control isn’t done correctly. We were trying to figure out the problem.

 

[quicksandfarmer]

One thing about your system is it must have RTK software built in, called an RTK engine. It's not just the hardware that makes this all happen but the software is an even bigger part of it.

The U-Blox chip contains a GPS receiver and RTK software in a single chip. If you look at this picture:

The blue square on the left is the radio transceiver to communicate with the other unit. The U-Blox chip is the metallic square on the right. All of the RTK calculations are done inside that chip. It's pretty amazing considering that chip sells on the U-Blox website for about $80.

Our new system, a Trimble has all of that plus a VRS system. With this we can use a hotspot to link up to the internet and use multiple bases tied into the system. Some states offer this service for free, in Illinois we have to pay for it, $2500 a years as I recall. With VRS you don't need a base.

There are free networks that transmit over the Internet but of course there aren't any with base stations near me. It seems like the base station has to be within 6 miles of the rover to get good accuracy. If I were going beyond playing with this I would ditch the radios and have the base and rover communicate over the Internet. The rover is attached to the smartphone and needs Internet access anyway to access the field definition map so the rover can communicate through it. I would set up a base station somewhere with a good view of the sky and Internet access within six miles of me and connect it to a free network. Then I'd have the rover access the free network through the smartphone.

For about $200 you can get a board that just has the U-Blox chip and jacks for USB and an antenna:
SparkFun GPS-RTK Board - NEO-M8P-2 (Qwiic) - GPS-155 - SparkFun Electronics

Once there's an Internet-connected base station nearby that board plus a smartphone becomes the price of admission.

There's also a newer version of the chip that's about $20 more:
SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic) - GPS-16481 - SparkFun Electronics

I haven't used it but this reviewer says it gives markedly better performance:
Comparing a uBlox F9P with a M8P with RTK - Blog - ArduPilot Discourse

 

[npalen]

That’s home plate on a baseball field. It’s a good example of when the model for machine control isn’t done correctly. We were trying to figure out the problem.

So who is on first? Sorry, couldn't help myself.

 

[s219]

So you get up to 6 mile range with the radio system between base and rover? That is great.

 

[quicksandfarmer]

So you get up to 6 mile range with the radio system between base and rover? That is great.

I haven't been able to test the range of the radio system but I doubt it's that far, I wouldn't be surprised if it was only a few hundred yards. The base has to be within six miles of the rover in order for the DGPS to be accurate.

 

[dodge man]

With a true VRS system (virtual reference station) the bases do not have to be close, although the closer they are the accuracy is better. With a single base the errors start to get larger the farther you get away from the base. Maybe 10 to 15 miles is the practical limit on a single base.

 

[dodge man]

I looked at the spec sheet and didn’t see anything listed for the radio. Typical is 1 or 2 watts. Even a 1 watt will probably go a mile. The higher you get the radio antenna the further the range. When we setup our 35 watt radio we often get the antenna 20 feet in the air. You need a license for this radio.

I noticed your unit does track Russian and Chinese satellites which helps for a quicker fix and allows for more obstructions.

 

[defranks]

Very interesting thread. I've been looking for an economical GPS that I can use to find my property corners. I know about where they are, but the survey lists one corner as having a pin, which I cannot find with a metal detector, and another as being a "stone". I found a painted stone using my old Garmin GPS, but I'd really like to have more accurate placement.

If I were to buy this U-Blox kit, will that give me everything I need to make it work?

(Couldn't link the URL, but a kit is available from Digi-Key, C94-M8P-2-10)

It looks like it has two of everything and comes pre-configured, but requiring some software downloads. The manual mentions "putty", and I have no clue what this, but I'm sure an internet search would turn it up.

Looks like the price may have come down, as this kit is $400 and includes two of everything, including ground planes.

 

[quicksandfarmer]

Very interesting thread. I've been looking for an economical GPS that I can use to find my property corners. I know about where they are, but the survey lists one corner as having a pin, which I cannot find with a metal detector, and another as being a "stone". I found a painted stone using my old Garmin GPS, but I'd really like to have more accurate placement.

If I were to buy this U-Blox kit, will that give me everything I need to make it work?

(Couldn't link the URL, but a kit is available from Digi-Key, C94-M8P-2-10)

It looks like it has two of everything and comes pre-configured, but requiring some software downloads. The manual mentions "putty", and I have no clue what this, but I'm sure an internet search would turn it up.

Looks like the price may have come down, as this kit is $400 and includes two of everything, including ground planes.

That's the exact kit I'm using. ****. I paid $800 from the U-Blox website for that same exact kit! (I actually paid $1200 because I dropped one of the boards and broke it and had to replace it.) I found that the ground planes in the kit weren't enough to give good results, I got better results putting the receiver on the roof of my car and then settled on using 18" pizza pans.

With that kit and a laptop you can get your location accurately, the limit is going to be how accurately you place the base unit.

 

[quicksandfarmer]

The manual mentions "putty", and I have no clue what this, but I'm sure an internet search would turn it up.

A long-winded explanation:

In 1874 Emile Baudot invented the teletype, which consisted of a pair of machines connected by wires where pushing a key on one machine caused a letter to be printed on the other. (The "Baud" used to describe modem speeds is named in honor of Emile Baudot.) When computers were developed it was quickly realized that it would be handy to have a way to get information into and out of them, and since teletypes already existed they were repurposed to connect to computers. When I first used a computer, in the 1970's, I would type on a teletype. When video screens and electronic keyboards were introduced it was easiest just to use the existing teletype interface so in the early days they were called electronic teletypes.

Over time the electronic teletypes got replaced with keyboards and monitors that connected directly to the computer. However, the teletype interface was still ubiquitous, so it was handy for connecting peripherals like printers and modems. As the interface became more general purpose it became known as the "serial interface." If you had a computer that didn't have an actual teletype, but wanted to configure one of those serial devices, it was handy to have a program on your computer that emulated the teletype. The most popular of those was named "TTY," short for teletype.

About 20 years ago the USB interface came along. Since the serial interface was so common at the time USB was made to be backwards compatible. GPS devices use the serial interface, although newer ones will only have a USB port.

So when you connect that DGPS device to your laptop or smartphone, it's essentially using the same interface that Emile Baudot created in 1874.

End of history lesson. The point of all that is you can connect to your GPS device using a TTY program, or "terminal emulator." I seem to recall that the kit came with one, it's probably the "putty" they're talking about. With a TTY you can communicate with the chip like you're using a teletype, you type commands and it sends back responses. The kit also comes with configuration software. It also comes with mapping software that takes the output from the chip and displays it on the screen. I only used the Windows versions, I don't know if there are other ones. When I started out with this I would connect the rover unit to the USB port on my laptop and walk around until the battery died.

 

[aczlan]

Very interesting thread. I've been looking for an economical GPS that I can use to find my property corners. I know about where they are, but the survey lists one corner as having a pin, which I cannot find with a metal detector, and another as being a "stone". I found a painted stone using my old Garmin GPS, but I'd really like to have more accurate placement.

If I were to buy this U-Blox kit, will that give me everything I need to make it work?

(Couldn't link the URL, but a kit is available from Digi-Key, C94-M8P-2-10)

It looks like it has two of everything and comes pre-configured, but requiring some software downloads. The manual mentions "putty", and I have no clue what this, but I'm sure an internet search would turn it up.

Looks like the price may have come down, as this kit is $400 and includes two of everything, including ground planes.

Putty is a windows program that gives you a text-based interface to talk to hardware of some kind.
Free and very easy to find online.

Aaron Z

 

[dodge man]

Getting a GPS system like you are looking at is probably not going to help you find your corners. Do you have coordinates for them? Probably not. Most surveyors work in state plane coordinates and the OP sounds like he works in lats and longs. I’m not sure if the OP has the ability to stake point or not? Say I’m surveying your property and find a corner. If the next corner is 500 feet away, i stake the first corner and walk roughly the correct direction until I’m 500 feet away. This narrows down the search area. I’m not sure if that’s possible with this type of system.

Long story short there is not a magic list of coordinates for property corners so GPS isn’t a magic box.

 

[s219]

Very interesting thread. I've been looking for an economical GPS that I can use to find my property corners. I know about where they are, but the survey lists one corner as having a pin, which I cannot find with a metal detector, and another as being a "stone". I found a painted stone using my old Garmin GPS, but I'd really like to have more accurate placement.

If I were to buy this U-Blox kit, will that give me everything I need to make it work?

(Couldn't link the URL, but a kit is available from Digi-Key, C94-M8P-2-10)

It looks like it has two of everything and comes pre-configured, but requiring some software downloads. The manual mentions "putty", and I have no clue what this, but I'm sure an internet search would turn it up.

Looks like the price may have come down, as this kit is $400 and includes two of everything, including ground planes.

How accurate do you need to be? How big is the property? Do you have clear line of sight to the sky? Can you see one corner from another? I have a hard time believing you need centimeter accuracy DGPS just to ballpark some corners. What I have done in the past is to combine standard GPS information with property line bearings to triangulate a corner. It always puts me within 6 inches of the pin.

 

[defranks]

I have a good idea where my corners are. My 20 acre, nearly square parcel is bounded on two sides by two intersecting roads, so the exact corner there is unimportant... the practical boundaries on those two sides are the two roads. One boundary is a state wildlife area, and it's roughly marked with paint on a line of trees. The two corners that interest me have been surveyed. One is supposed to have a pin, but I was unable to find it. The other is a "stone", and sure enough, there's a painted stone along the property line I share with the state, right where my GPS said it should be, within the error of the GPS.
There's a property marker across the road from the corner with the missing pin, but it's not got a surveyor's cap on it, it's a painted "T" post, but I believe it's pretty close based on my GPS and measuring from corner at the intersection of the roads.
I think, but am not certain, that my boundaries are recorded with lat and long coordinates. I'll have to dig out the document to be sure. Three of the corners are on roads, so I have a pretty good view straight up, but there are trees on both sides. That fourth (the painted stone) corner is in the woods, but my handheld GPS has reception there.
Thank you all for the input! It's much appreciated. I may just buy that kit to have it, I'm a ham radio operator, fly model airplanes, and bought a hand-held GPS WAY back when they first became generally available and were WAY too expensive. In other words, I like my gadgets.