Somewhat accurate device for mapping

[JohnyBeGood]

Hi all!

 

Due to current economy our projected budget for GPS device has shrunk.

Basically we need device to record somewhat accurate latitude and longitude (< 3m) of certain location that later on if needed be easy found using lat. and lon. info.

I now that accuracy is driven by price, which brands/models would get us best bang for the buck?

Budget is up to $1000

 

Any help is much appreciated!

Edited March 5, 2009 by JohnyBeGood

[+PDOP's]

The best accuracy you can expect from any recreational grade GPS receiver is +/- 3 metres (10 ft) under ideal conditions. Under tree cover or in difficult topography accuracy will be much worse.

[yogazoo]

My consumer grade suggestion - Garmin 60CSX - Street price $300

 

It is what our state department uses to map out irrigated fields, water diversion points, irrigation ditches and other places of interest. The data we collect using the 60CSX is always amazingly accurate and meets GIS/legal quality/accuracy standards. Our budget has shrunk too and any hopes of Trimbles in our future went out the window a while ago. Not only that but anyone can pick up this unit and in a relatively short time figure out how to use it. Unlike the Trimble's.

 

Your budget would allow for three to be purchased.

 

One more thing about the Garmin brand. Maps can easily be made from any GIS shapefile dataset (points, lines, and polygons). One map that I made for these state GPS's is a legal land description map that shows on the map screen which Township, Range, Section, and QuarterQuarter the user is in. Very handy for obtaining legal information at-a-glance. I digress.

Edited March 5, 2009 by yogazoo

[+DavidMac]

I now that accuracy is driven by price, which brands/models would get us best bang for the buck?

Budget is up to $1000

 

Actually, that's note quite accurate when considering consumer grade handheld GPS receivers. Usually, the difference in price is due to extra features which won't affect accuracy such as auto routing, topo maps, or a larger display. So long as your GPSr supports WAAS (as most models these days should, I believe), you won't get much greater accuracy out of a $600 Nuvi than a $100 etrex. Granted, some models use different antenna types which may vary slightly in accuracy, but you'll never get better than about 3 m with a typical handheld unit. If you need more than that, you'd need to look into something like a survey grade GPS (such as those made by Trimble) and those will cost you well over $1K.

[CURTISANDLACEY]

There are a few factors to consider.

 

Are you looking for a unit with maps? If so, do you need the maps and what kind? This will add to the total cost and will make a difference on the unit. Each company that makes handhelds have their own maps.

 

A handheld unit that has an accuracy under 10ft is hard to find and is very price driven. In these forums most people are using standard handhelds with real world accuracy of anywhere from 60ft to 20ft. (This will spark debate with many people who will say that their handhelds shows them a better accuracy which is indicated on the unit. This once again is not the true ground accuracy of the unit.) I currently work for a surveying company which uses "Survey" Grade GPS's. The accuracy of these units are 2cm +or- 1 part per million and require at least 2 units. One for a base station and One for a rover. (these units cost around $20,000 per unit) All that being said, what type of data are you trying to collect?

 

Any other information would help us to help you.

 

Here are the standard handheld units I would suggest:

 

Garmin 60 series because of their high accuracy quad helix antennas with real world results of 10ft-20ft +or- 5ft. Another I would suggest is the new Garmin Oregon which has a new antenna that Garmin has not released the info on yet, but I have been checking my new Oregon against Survey Grade control points and have been getting results in the 15 ft range with the unit saying it has an 18ft accuracy(with no tree canopy). So if I had to guess I would say this unit is in the 10ft-20ft +or- 5ft range like the quad helix antennas.

[JohnyBeGood]

First of all thanks for the replies!

 

I'll try to answer couple of questions.

Originally we were thinking to get Trimble GeoXT 2008 that in the beginning would be used for to record "exact" locations of meters (lat. + lon.) in the ground and then later on utilize it to the full extend with maps.... etc.

So for now we need only one GPS device to record most accurate lat. + lon.

I was researching Garmin and I came accross this site http://www.gpsinformation.org/penrod/g60csx/60csx.html that says 60CS is more accurate then 60CSx (11 vs. 21FT).

So far I have choices of:

- Garmin 60CSX

- Garmin Oregon 400t

 

I hope I answered all of the questions

[egorny]

My consumer grade suggestion - Garmin 60CSX - as well

Doing some serious mapping with it for to use with a GIS application.

So I got the unit but added an external antenna from Garmin that is used for boats. You have to also get the reducer cable to work with the external mount of the GPS 60,

 

Placed the antenna on a pole, comes with a long cable.

Every bar was at the Max reading with it.

 

Ed

[+julianh]

 

I was researching Garmin and I came accross this site http://www.gpsinformation.org/penrod/g60csx/60csx.html that says 60CS is more accurate then 60CSx (11 vs. 21FT).

Don't make the mistake of believing that the EPE as displayed on the unit is the same thing as your ACTUAL accuracy. It is only an estimate of the positional accuracy, and Garmin don't even specify precisely what it is reporting. Garmin may even have changed the algorithm for calculating the displayed EPE between different models, and maybe even between different software upgrades on the same model. Use the EPE as a rough guide only.

 

The best guess around here is that it the EPE is something the like the 50% confidence radius; that is, if the unit shows an EPE of 5 metres say, the unit is estimating that you have roughly a 50% chance of being within 5 metres of the displayed location, and about a 50% chance that you are more than 5 metres from the displayed location. There is no real theoretical upper limit to how far away you could actually be, but there is a pretty good probability (say 90% or so) that you are within approximately 2 to 3 times the displayed EPE of the displayed location.

 

All things being equal, any current generation consumer GPSr with high sensitivity receiver (e.g. 60 CSx, eTrex H series, etc) will give as good or better location accuracy almost all of the time than any older model without a high sensitivity receiver (e.g. 60 CS, eTrex non-H series, etc). In practical terms, there is not really any difference in positional accuracy between the cheapest current generation high-sensitivity receivers (e.g. yellow eTrex H) and the top of the range consumer models (e.g. Oregon 400, 60 CSx, etc). the extra price buys you more features, but not more accuracy.

 

Hope this helps!

[JohnyBeGood]

Thank you all for the replies!

 

You're right julianh when it comes to consumer models extra price will only buy us more features.

I think Garmin 60CSX is the best solution for us right now. Hopefully one day will be able to get Trimble GeoXT.

One more dumb question, from what I've read every GPS device will be able to display current position in lon. + lat. so will 60CSX?

Just want to make sure.

[egorny]

Ed here again. With the GPS 60 Csx (without the external antenna), we used it to determine the appox lot line for some porperty we purchased. The east side of the lot is about 750 feet long and I knew the corner posts. So I GPSed them and then using the electonic compass and go to function we determined the appox location of the lot line. It did go into a very dense woods as we as in a ravine.

After a lot of clearing (honey suckle) we had the area professional surveyed. As we were placing posts along the line we kept coming across the red flags we placed when we GPSed thee area. To the surveyors surprise, in most cases I was within 10 - 16 inches of the true line except for one point which was right on.

 

I wish I had the external antenna, propbably would on been closer.

 

Ed

[+JBnW]

One more dumb question, from what I've read every GPS device will be able to display current position in lon. + lat. so will 60CSX?

 

A'yep. And in multiple coordinate formats (D.M.S., Decimal Minutes, Decimal Seconds...) and just about every Datum known.

[+PDOP's]

One more dumb question, from what I've read every GPS device will be able to display current position in lon. + lat. so will 60CSX?

The short answer is yes This is a standard feature on almost all recreational receivers and the coordinates can be displayed in a variety of formats. There will be a wide selection of datums too.

[+Rockin Roddy]

I would add that my DeLorme PN-40 has seen 5' (not meters) of accuracy several times, it's normal to see! The PN-40 is said to be as accurate (or even more accurate in my opinion) than the 60CSx, but allows for a LOT more bang for the buck (around $320...with maps included).

 

Food for thought!

[+mattalbr]

...snip

Food for thought!

 

Someone is liable to get a stomach ache from that food.

 

To the OP, if you are going to be out in country with few obstructions a recreational grade rx may suit your needs. If you're going to be in an urban environment I'd suggest stepping up in rx grade. You can acquire used equipment which reduces cost a bunch. It sounds like you work for a gov agency of some type. At most local levels there should be a survey department or something like it. Maybe get in touch with them to see about using their equipment. It must be said that the results of using better equipment are limited to the quality of your post-processing solution...which is both an art and a science.

 

 

Matt

Edited March 6, 2009 by mattalbr

[+Rockin Roddy]

I would add that my DeLorme PN-40 has seen 5' (not meters) of accuracy several times, it's normal to see! The PN-40 is said to be as accurate (or even more accurate in my opinion) than the 60CSx, but allows for a LOT more bang for the buck (around $320...with maps included).

 

Food for thought!

 

5 feet compared to what? It's not measuring against a known point on the ground. These recreational grade receivers (ALL brands) can't reliably and consistently get you within 5 feet without some type differential correction post-processing. They're single channel units and that's the bottom line. Doesn't matter what the thing is telling you. They're all fine units but have their limitations regarding both accuracy and precision...hence the term 'recreational grade'.

 

The OP may be able to get a used mapping grade or, better yet, a survey grade setup. If the intention is to add the data into an entity's GIS I'd steer clear of recreational grade units. The only time I've used a recreational grade rx to collect data for a GIS was in 2000. Was working for a county auditor's office as a GIS analyst. We used a Garmin GPSIII+ linked with a digital camera to get a photo of each structure in the county and general position of where the photo was taken. Took an enormous amount of time after data collection to get the points (measured locations) into the proper polygons (parcels). Had to be right though because it was going to be used by EMS.

 

Sorry, I saw some touting how accurate the 60CSx was (someone said 11') and I reported my accuracy. So, to answer your question, it's reading 5' instead of 11', or 5' for the PN-40 as opposed to 11' for the 60CSx! Since many believe the 60CSx to be very accurate, I wished to point out the PN-40 has been said to be AS accurate or better by more than a few users!

[+Rockin Roddy]

The best accuracy you can expect from any recreational grade GPS receiver is +/- 3 metres (10 ft) under ideal conditions. Under tree cover or in difficult topography accuracy will be much worse.

 

As I have already reported, the PN-40 I use has seen 5' accuracy more than a few times, so this statement isn't completely accurate! Now, whether the reading was accurate or not, I couldn't tell you, but it does seem very accurate to me!

[+Rockin Roddy]

 

Here are the standard handheld units I would suggest:

 

Garmin 60 series because of their high accuracy quad helix antennas with real world results of 10ft-20ft +or- 5ft. Another I would suggest is the new Garmin Oregon which has a new antenna that Garmin has not released the info on yet, but I have been checking my new Oregon against Survey Grade control points and have been getting results in the 15 ft range with the unit saying it has an 18ft accuracy(with no tree canopy). So if I had to guess I would say this unit is in the 10ft-20ft +or- 5ft range like the quad helix antennas.

 

It's not a new antenna, it's the chipset (or so I've been told), and the Garmin OR has been reported to have very spotty accuracy! Some would say they're spot on while many more have reported (and shown proof of) their units being very jumpy. I wouldn't recommend this one just yet!

 

This was also true of the PN-40 until the last update, now I am seeing great tracking and a nice 5' accuracy often!

 

To take this a bit further, I would recommend the 60CSx over the OR or CO. The 60CSx has been a proven accurate GPS (but, remember that I have also stated the PN-40 has been shown to be AS accurate or better in many cases).

Edited March 6, 2009 by Rockin Roddy

[+PDOP's]

Now, whether the reading was accurate or not, I couldn't tell you, but it does seem very accurate to me!

The only valid accuracy test are waypoints taken on a survey benchmark with known coordinates. Anything else is at best a general indication. As others have said, the accuracy reported by receivers (EPE or otherwise) are just figures of merit and are not to be taken as an absolute.

[+Rockin Roddy]

Now, whether the reading was accurate or not, I couldn't tell you, but it does seem very accurate to me!

The only valid accuracy test are waypoints taken on a survey benchmark with known coordinates. Anything else is at best a general indication. As others have said, the accuracy reported by receivers (EPE or otherwise) are just figures of merit and are not to be taken as an absolute.

 

Right, that's why tracking is brought up. I base my opinion on the tracks I have seen and made. If the tracks are way off on a out and back trek, I'd say the accuracy is spotty. If it tracks almost right on top of the other track, I'd call this fairly good accuracy.

 

The PN-40 has been shown to track closely as has the 60CSx.

 

Truly, unless the OP is going to buy a commercial grade GPS, what else are we talking here but best general indication??

[+mattalbr]

Sorry, I saw some touting how accurate the 60CSx was (someone said 11') and I reported my accuracy. So, to answer your question, it's reading 5' instead of 11', or 5' for the PN-40 as opposed to 11' for the 60CSx! Since many believe the 60CSx to be very accurate, I wished to point out the PN-40 has been said to be AS accurate or better by more than a few users!

 

No need to be sorry, man! We're all in this together.

 

Matt

[+Rockin Roddy]

Sorry, I saw some touting how accurate the 60CSx was (someone said 11') and I reported my accuracy. So, to answer your question, it's reading 5' instead of 11', or 5' for the PN-40 as opposed to 11' for the 60CSx! Since many believe the 60CSx to be very accurate, I wished to point out the PN-40 has been said to be AS accurate or better by more than a few users!

 

No need to be sorry, man! We're all in this together.

 

Matt

 

There's a benchmark at the golf course we own, I will check the PN-40's accuracy when I get a chance! Will the benchmark have the coords on it (can't remember since it's been a long time since I last looke at one)?

[+randyrucker]

I like the idea of having a patch type antenna. I think it is a little more sensitive receiving the satellite signals. If accuracy was the most important thing in a consumer grade unit I would look for the newest gen chipset in a unit with a patch type antenna. The 60Csx and PN-40 have this type of antenna and both have been reported to have great accuracy. I don't know about the Oregan since I don't own one but people who do say its very accurate also. Those three units are what I would consider getting. I have checked my PN-40 on several benchmarks and one was off by 0.62 feet and the other was off by 1.88 feet. Maybe not a scientific sample, but I was just curious how close it was to a highly accurate survey plot latitude, longitude position.

Edited March 6, 2009 by randyrucker

[+PDOP's]

If accuracy was the most important thing in a consumer grade unit I would look for the newest gen chipset in a unit with a patch type antenna. The 60Csx and PN-40 have this type of antenna ...

Actually the 60CSx has a quadrifilar type antenna. There used to be considerable debate about which type is the best (link) but I believe having a high sensitivity chipset is more important these days.

[CURTISANDLACEY]

 

It's not a new antenna, it's the chipset (or so I've been told), and the Garmin OR has been reported to have very spotty accuracy! Some would say they're spot on while many more have reported (and shown proof of) their units being very jumpy. I wouldn't recommend this one just yet!

 

This was also true of the PN-40 until the last update, now I am seeing great tracking and a nice 5' accuracy often!

 

To take this a bit further, I would recommend the 60CSx over the OR or CO. The 60CSx has been a proven accurate GPS (but, remember that I have also stated the PN-40 has been shown to be AS accurate or better in many cases).

 

You might be right on the chipset vs. the antenna being new on the Oregon, I will have to check this. That being said your next statement about the PN-40 and seeing great tracking since the last update is also true with the Oregon. The PN-40 and the Oregon uses the same chipset and receive updates from the chipset manufacturer at the same time, and I am seeing the same result with the Oregon. Both units are using the STM Cartesio Chipset. The PN-40 is using the 32 channel model and the Garmin is using the 12 channel model.

 

Oregon chipset: http://garminoregon.wikispaces.com/GPS+Receiver

PN-40 chipset under detailed specs: http://shop.delorme.com/OA_HTML/DELibeCCtd...p;section=10461

[+coggins]

Both units are using the STM Cartesio Chipset. The PN-40 is using the 32 channel model and the Garmin is using the 12 channel model.

Are you saying that is a 12 channel version of the STA2062?

[CURTISANDLACEY]

Both units are using the STM Cartesio Chipset. The PN-40 is using the 32 channel model and the Garmin is using the 12 channel model.

Are you saying that is a 12 channel version of the STA2062?

 

I think I stand corrected. All I can seem to find is sellers websites saying 12 channels on the Oregon. Garmin.com doesn't say anything about it. Then the chipset manufacturer's website says its a 32 channel. The Garmin users book for the Oregon says "More than 12 channels". I think I will send Garmin an e-mail and see what they say. Thanks coggins for catching that.

[CURTISANDLACEY]

Here is why I was thinking that the Oregon is using a new antenna.

 

http://garminoregon.wikispaces.com/Hardware

 

I can't seem to find any information on the exact type of antenna, so if anyone knows jump in.

 

Back to the OP:

I am told that the GeoXT is a great little unit, but to get the sub meter accuracy you need to post process the data. Which usually means you have to buy post processing software in addition to the unit. Post processing software can be VERY technical. So there is a big learning curve when you get into this type of software. There are things like setting up the proper coord system, manually adding your Geoid files, proper operation of the data collector and PP software. All of this takes time to learn and may add an additional cost to training when it is all said and done.

[+myotis]

As others have mentioned while a GPS may say something like 5 foot accuracy that by no means indicates you are within 5 feet of the reading. Recreational GPS simply are not that accurate. A broken clock is right twice a day-so sometimes you are right. You could have a reading of 50 foot accuracy and be exactly right. You have to get survey grade equipment to get that kind of accuracy. Also remember comparing your to and from track is not a good comparison. You have basically the same atmospheric conditions and same satellite geometry when you return so you will have simular errors. So a better comparisons is coming back a week latter.

 

One should also remember you do not need survey grade accuracy for many things. For almost anything even 25 foot accuracy will get you close enough to see what you are looking for. Look how good some of us do finding geocaches. If you are mapping a trail for us on your GPS. For example if you want to map a trail for your GPS, 25 feet accuracy is more than adequate-50 foot would also normally be sufficient. The only exception is when you have a maze of trails real close.

[+Rockin Roddy]

As others have mentioned while a GPS may say something like 5 foot accuracy that by no means indicates you are within 5 feet of the reading. Recreational GPS simply are not that accurate. A broken clock is right twice a day-so sometimes you are right. You could have a reading of 50 foot accuracy and be exactly right. You have to get survey grade equipment to get that kind of accuracy. Also remember comparing your to and from track is not a good comparison. You have basically the same atmospheric conditions and same satellite geometry when you return so you will have simular errors. So a better comparisons is coming back a week latter.

 

One should also remember you do not need survey grade accuracy for many things. For almost anything even 25 foot accuracy will get you close enough to see what you are looking for. Look how good some of us do finding geocaches. If you are mapping a trail for us on your GPS. For example if you want to map a trail for your GPS, 25 feet accuracy is more than adequate-50 foot would also normally be sufficient. The only exception is when you have a maze of trails real close.

 

THANKS for the friendly post, my friend! I agree with differing times for tracks, that would be optimal.

[CURTISANDLACEY]

Both units are using the STM Cartesio Chipset. The PN-40 is using the 32 channel model and the Garmin is using the 12 channel model.

Are you saying that is a 12 channel version of the STA2062?

 

I think I stand corrected. All I can seem to find is sellers websites saying 12 channels on the Oregon. Garmin.com doesn't say anything about it. Then the chipset manufacturer's website says its a 32 channel. The Garmin users book for the Oregon says "More than 12 channels". I think I will send Garmin an e-mail and see what they say. Thanks coggins for catching that.

 

OK, for those following this 12 channel thing this is the response I got from Garmin. The question I asked was how many channels and what type of antenna does the Oregon have.

 

"Thank you for contacting Garmin International. I will be happy to help you with this. The Oregon is a 12 Channel GPS, and the Antenna is called a Ceramic Antenna. It is a chip antenna that much smaller than most quad helix and patch antennas."

 

What I am getting with my Oregon is 12 GPS sats + 1 WAAS sat so does this make it 13 channels or 12 channels + 1 WAAS. I don't know.