Gps And Topographic Mapping From Data

[+Northern Trekker]

For those out there with the knowledge, I need your advice:

 

I have purchased some land and now I would like to get a topographic map of that land to plan for the house we will be building. I would like to do that using the data that I can collect with my GPS. Here are the details:

 

The land is 45 acres in size and is mostly clear of trees (reception is good).

I have a Garmin MAP 76 S that I will be using to collect data.

I do not currently have any special mapping software (like AutoCAD)

I do have Mapsoft so I can download the local maps to the GPS.

 

Here are my questions:

Has anyone out there done this?

How did you go about doing it? (I assume I would place the GPS on the ground to get a reading or have it at a fixed elevation above the ground, like waist level)

Did you get good resolution?

I assume I would do this with WAAS enabled.

What software should I invest in (buy)?

 

Anything else you can do to help me would be greatly appreciated. I would rather do this than hire a surveyor to topo the land (if this is possible).

 

Thanks in advance for all your help and advice!

Northern Trekker

[CenTexDodger]

Yes you can do what you are describing, but you just have to realize that you are not going to get survey grade accuracy. That being said, if you do it in one day you elevation readings should be fairly accurate relative to each other. So , if you start from a known elevation, you should get pretty good readings.

[+Mopar]

It would probably be a LOT easier to just use the GPS to get the coords of the boundaries of your property and then use them to plot your area on commercially available topo maps.

[stevesisti]

For those out there with the knowledge, I need your advice:

 

I have purchased some land and now I would like to get a topographic map of that land to plan for the house we will be building. I would like to do that using the data that I can collect with my GPS. Here are the details:

 

The land is 45 acres in size and is mostly clear of trees (reception is good).

I have a Garmin MAP 76 S that I will be using to collect data.

I do not currently have any special mapping software (like AutoCAD)

I do have Mapsoft so I can download the local maps to the GPS.

 

Here are my questions:

Has anyone out there done this?

How did you go about doing it? (I assume I would place the GPS on the ground to get a reading or have it at a fixed elevation above the ground, like waist level)

Did you get good resolution?

I assume I would do this with WAAS enabled.

What software should I invest in (buy)?

 

Anything else you can do to help me would be greatly appreciated. I would rather do this than hire a surveyor to topo the land (if this is possible).

 

Thanks in advance for all your help and advice!

Northern Trekker

Not sure what you are after, but there are dem (digital elevation Model) maps available for free on the internet. Problem is you then need software to view and interpret the data. Global Mapper has trial software you can dwonload and then find out if DEM data is available for your area.. In GM, you can color code different elevation levels so you can graphically see a general over view of your land....global mapper will also generate contour lines at elevations of your choosing, along with allowing you to "overlay" data from other maps. This however could turn out to be quite a project, and become somewhat involved. Were you to generate your own data, it would be a "really" big project, and certainly more than is required for locating a home site.

 

Personally, If I had 45 acres, I would use the GPS to mark off the corners or boundaries, visibly mark them, and then I would walk the land...45 acres is a nice size but certainly is not too big to become easily familiar with. Also, no amount a mapping and elevation data is a substitute for standing on the terra firma and taking a good look around at the different views from different locations on the plot. Especially if your main effort is to decide the exact location to build a house.

[+Northern Trekker]

Thanks for the info so far,

 

Here is some more info to fill in a couple gaps:

 

The land is in Kentucky and I am in Alaska. I have the opportunity to get to the land about every other year. I am hoping to work on site plans in Alaska during the time I am not in Kentucky.

 

See my dilemma?

 

I need relative elevations. I have found a recent (1998) aerial photo of the land that is fairly good resolution, however I still would like to get a better than USGS topo.

 

Thanks for the info to this point. More is ALWAYS APPRECIATED!

 

Northern Trekker

[+1setter]

I think the problem would be with the accuracy of the altitude readings with our consumer GPS receivers. Waypoint marked and shot with a transit would be much more accurate. A transit and stick could be rented at almost any tool rental place. Learning how to use it might be another matter, but it's not really that hard.

[+raouljan]

You could take the DEM data and make a custom map for you Garmin.

http://gpsinformation.net/gpsmapper/gpsmapper.htm

 

This is a heck of a lot of work and will be complicated by the resolution of the DEM and the accuracy of the GPSr (even with WAAS on).

 

You can get very high accruacy with DGPS... and you can ake your own DGPS receiver.

http://www.abnormal.com/dgps/

again .. a lot of work.

 

One of the things I found works well is to download the DEM, import it into something like Azi Explorer and use that map for your waypoint, routes, etc.

 

Again, resolution and accuracy are going to be your major headaches.

[+raouljan]

Until you get to the trig

[+Northern Trekker]

I am a Civil Engineer and have operated many a level, however I was looking for something I could record all the data at once. I suppose I could rent a Total Station and do it that way (it records the angle, both horizontal and vertical and calculates the location and elevation AUTOMATICALLY) however, I wanted to use the GPS and invest in some software that I could use on my laptop / desktop machine to do the planning.

 

I was hoping that someone with current experience would see this note and give me some straight-up advice.

 

Still looking for the software / GPS solution to this ....

 

Thanks to all so far.

 

Northern Trekker

[Wild T2]

I recently did an elevation accuracy assessment using a Garmin GPSMap 76.

 

I observed points at the same elevation 35 times. Here are the results…

 

Count: 35

Mean: 761.49

Maximum: 777.00

Minimum: 753.00

Range: 24.00

Variance: 35.67

Standard Deviation: 5.97

 

Conditions were more-or-less wide open skys, WASS differential corrected, and at different times of the day over several days.

 

I think that using the GPS for X and Y and an inexpensive laser level for Z would work out better than GPS only for X, Y, & Z.

[+Mopar]

You're getting lots of answers between your duplicate posts (what does this topic have to do with "Here educators can share and discuss ways to use GPS technology in education." anyway?), you just don't seem to like the answers.

You have enough hides/finds to know that even with WAAS, consumer GPS just isn't THAT accurate. How often do you find a cache where your GPS says it should be, vs how many times the GPS is still pointing 25-50ft away? GPS was really designed for horizontal accuracy, not vertical, so even if your consumer GPS is only 30ft off horizontally, it can still be off 50ft or more vertically. This is explained in detail on many websites, including ones already linked in the other thread. Try this one.. I've had a few occasions to compare my GPS to a vertical benchmark, and it's not unusual for the GPS to be 100ft off on the hight. Certainly not good enough for building topo mapping purposes.

[+Northern Trekker]

T2 (great name by the way)

 

Thanks for this info! What you have done is answered a LOT of my questions with your data.

 

I will forgo the elevation info, even though I think I can cover the entire site in 4 hours. I will shoot the site with a reglar level and add those to my waypoints afterward.

 

I still do not know what software would be best to generate my topo map in the end. Any ideas?

 

Thanks,

Northern Trekker

[+Northern Trekker]

Mopar,

 

You are right. I have learned a lot here during this discussion and after getting the data on 35 readings at the same location with a +/- of 24 feet, I have resolved to do the vertical the regular way (with a level).

 

Yes, I was reluctant to accept this final answer, hoping for better news, but that is because I was thinking that someone out there may have "discovered" something that I was unaware of.

 

I filed this under education in case someone in the education field had some experience with this. Again, sorry if this duplicated postings.

 

I appreciate everyones input and helping me determine my final solution.

 

Thanks a bunch!

 

Northern Trekker

[+Renegade Knight]

Here are your options.

 

1) AutoCAD or Microstation with the add ins to do topo.

2) Pencil and Paper (aka the old fashioned way)

 

You should of done 2) in school and I'm not sure it will help you unless you are going to desing your house the old fashioned way as well.

[+Renegade Knight]

I forgot, if you are lucky, you can scab off work done by others in the same area. If for example your land is near a highway and they have flown it and run a topo along the highway. Normally though the band they look at is too narrow. However the arial photo company might have a wider perspective and for a 'nominal fee' get you squared away.

 

Since all you need is a hack topo you can also hire a hack firm to whip one out. It doesn't really sound like your land would take all that long to topo.