Spatial Analysis / GIS / Export X-Y

[Yeasty]

Today I decided to see whatever differences there are between my Garmin Dakota 20 GPS and the embedded GPS in the CTX. It was quite an eye-opener.
I took a screen capture from Xchange 2 and overlayed and aligned it onto Google Earth.Then I downloaded the Garmin track into GE. Then I did another screen capture from GE for the attached picture.
The Garmin track is in blue and the CTX track is in yellow. The sharp southwest spike in the Garmin track is probably from it temporarily losing the satellite signal.
As you can see, the CTX GPS track is much more detailed than the Garmin and seems to be much more accurate. The sample rate for the Garmin was set at 30 seconds and could be somewhat enhanced if lowered to 10 seconds. I have no idea what the sample rate for the CTX GPS is. You would think there would be much more alignment of the two tracks.
I am very, very impressed with the CTX GPS accuracy and performance.

 

[Jason in TN]

Did you find any thing on the roof of that house? Sorry had to ask. Thanks for the test.

Jason

 

[Yeasty]

That house was torn down a few years ago. It's open space now.

 

[C&RHunter]

Yeasty, Thanks for your test comparisons. I don't have a handheld GPS to perform a test like you did. I have found that if you layout a grid pattern that you can retrace, and then make multiple "Hunts" on that pattern, your CTX patterns will not overlay "perfectly". But for metal detecting, the CTX will usually get you to within a few feet, and that is better than trying to find a spot like this: "okay I was x number of feet from the oak tree and x number of feet from the elm tree....What the --- the trees aren't there anymore!!". I have been very pleased with the GPS feature.
I have done some testing with "GO TO" function in the CTX, also. I wanted to find out how it would repeat. I set some nails out in my pasture saved their locations. I will go out at different times of day and on several days, and use the "GO TO" function to go to the nails. I am usually within 10 feet or less of the nails, occasionally some farther,but nothing way off. I also got known Lat and Long coords from a USGS data sheet for a monumented USGS benchmark not far from my house. The CTX put me 8 feet from the benchmark. I haven't gone to it but one time, but was very satisfied with that result.

 

[Gonehunting]

I have a DeLorme Earthmate PN 40 That I used religiously.. It stays at home now.. I also noticed late in the day tracks seemed to be off on the DeLorme.. don't know why but when I came back in the morning track was over 15 yrds off to the east.. every time... Just my observation.... Selling the Pn 40...good graphics but doesn't seem as precise as the X..

 

[grouser]

looks like you jetted off to the liquor store there!!!!!,,,,, and just a note,,,, ALL consumer level GPS devices are purposely inaccurate due to intentional error imputed by the military ( the satellites belong to them),,,, if you get down to 3 meters that's as good as you can expect,,, and even worse or turned off if there are security threats to the country

 

[nick777]

Is there a way you can export your point data to a spreadsheet, table, database or even delineated text format? Yeah, I could drag a GPS around and do this, but it is integrated into the CTX3030 (just ordered one and waiting on it) so I'd like to understand how you can work with the GPS data. Any data on the accuracy & precision of the GPS would be appreciated as well.

I'm a geospatial analyst and I'd like to be able to do some spatial interpolation to make some heat maps with ArcGIS to detect hot spots after heavily hunting an area. Plus, it would make some great graphics for the forum.

 

[C&RHunter]

Nick, here is a link referring to accuracy comparisons. This is probably not as detailed as you want, but may give you an idea of how accurate it seems to be and it's uses. If you haven't, you can do a search for GPS and there will be several threads come up that have discussions on the GPS feature....HH

http://www.findmall.com/read.php?86,1729384,1729414,quote=1#REPLY

 

[nick777]

Grouser, that used to be true, but the civilian and military signals are now the same accuracy. The M code does have some security enhancements, but eventually they will be the same in all respects. With post-processing, you can get sub-centimeter accuracy on survey grade units with differential correction. Units that can connect to other GNSS systems (GPS being one, GLONASS another, BEIDOU and Galileo the other) can boost accuracy a bit by increasing the number of sattelites.

Of course, you can't do this on the metal detector. I mean, there might be a way to collect 30+ points without moving with the detector, then export the points to a program like Trimble Pathfinder GPS and run a differential correction, but it would probably be a pointless exercise as far as treasure hunting goes. I'd guess that about 3m with the detector does sound reasonable.

http://www.gps.gov/systems/gps/performance/accuracy/

 

[Yeasty]

Unfortunately you cannot export GPS track or point data except to Google Maps via Xchange 2. It would be so much better to be able to take the raw data and be able to lay it into Google Earth where you can view multiple tracks (hunts), historic overlays etc. That's the biggest gripe I have about the CTX GPS. Obviously all the data is stored in the machine but I dont have the programming skills to extract it.

 

[C&RHunter]

Unfortunately you cannot export GPS track or point data except to Google Maps via Xchange 2. It would be so much better to be able to take the raw data and be able to lay it into Google Earth where you can view multiple tracks (hunts), historic overlays etc. That's the biggest gripe I have about the CTX GPS. Obviously all the data is stored in the machine but I don't have the programming skills to extract it.

In the XChange2 app. the GeoHunts can be viewed in the App on Google Maps. If the hunts are stored in the same collection, they will all be displayed at the same time. By placing the cursor over each individual Hunt, in that collection, that hunt will change to a different color. By clicking the edit button on a specific Hunt, the specifics of that single hunt will be shown in a pop-up box. Also, by using Print Screen function on the keyboard, and then Paint to edit, I have saved the picture, of a multiple or singe GeoHunt as a jpg, and then overlaid that onto Google Earth. The overlays are saved there, so then they can be clicked off or on whenever desired..................

 

[ironman200081]

Good information. I am also a bit bummed that Xchange2 cannot export raw GPS data, but I concur that the GPS location plotter on the CTX is very accurate.

Is there a favorite GPS plotting program that any of you all have used in the past? I would like to take the LAT/LON and spend the time to manually plug it in to another program so that I can plot where the "shot" bullets were compared to the "dropped" bullets on my Civil War skirmish site. I hope to do a presentation on the results for the community. Any advice?

 

[Yeasty]

I'd like to be able to do this with the CTX's GPS track data. What you see is a 1937 aerial photo overlay of an old farm site on Google Earth with the tracks and finds locations from my Garmin Dakota 20. You cant do this with the CTX data.

 

[C&RHunter]

It can be done in a fashion. The tracking of various Hunts will all be one color, the finds won't have specifics on them but the indicator can be displayed. This was done by creating an overly of the GoogleMap image, in addition to an 1907 map image, both overlaid onto Google Earth. It is more complicated this way, but somewhat similar results can be obtained. However, if it was possible to export the CTX results in a format usable by another program, it would be nice...........

 

[Yeasty]

It would be really really cool if a site overlay could be downloaded to the CTX like this.

 

[nick777]

Hrm. I see some people saying you can export the KML from Google Maps to Google Earth. If you can pull the KML out, you can translate it into other formats if you have GIS software. So, now I'm wondering if you can upload fake locations into the CTX. I'm thinking of taking historical maps, georectifying them to current maps based on aerial photos, drawing a boundary which to search on, then uploading that boundary into the CTX. You could define places that no longer exist but are just pieces of a big field.

Can you upload to the CTX? I plan on doing a little bit of hacking with the GPS features, but for now I'm trying to learn the basics of the machine... just got it in today and im PUMPED!

 

[nick777]

Well, you can export from Google Maps to Google Earth, but the XChange2 app seems to be a mashup and I don't see how to export the KML. There may be a way though. I'm working on it.

Normally to get data from Google Maps to Google Earth: Sign in to Google Maps and add your data.Save it to My Saved Places. Then, click the KML button. This stands for Keyhole Markup Language - a long time ago, Google bought a company named Keyhole and uses their technology in their mapping applications. So, you download this *.kml file to your computer, then open up Google Earth and just click and drag the file onto the globe. You'll zoom into your data.

 

[C&RHunter]

Hrm. I see some people saying you can export the KML from Google Maps to Google Earth. If you can pull the KML out, you can translate it into other formats if you have GIS software. So, now I'm wondering if you can upload fake locations into the CTX. I'm thinking of taking historical maps, georectifying them to current maps based on aerial photos, drawing a boundary which to search on, then uploading that boundary into the CTX. You could define places that no longer exist but are just pieces of a big field.

Can you upload to the CTX? I plan on doing a little bit of hacking with the GPS features, but for now I'm trying to learn the basics of the machine... just got it in today and im PUMPED!

If you do an overlay of a historical map in Google Earth, you can then get the Lat and Long from each corner of your proposed search area or to an old structure. Then in XChange 2 you can make new way points using those Lat and Longs. Then just put the Way Points into the CTX and head out. It's not exactly what you were talking of doing, but will get you there. It may not put you on the front porch, but you should be in fairly close proximity to the old structure location..HH