I make my living working with online maps and property lines. Hopefully the following info will shed light.
1. Online Gmap4 map with federal boundaries
One of my projects is
Gmap4 which is an enhanced Google map viewer that I developed. I have posted about it before here in the OYOA forum. The following link:
Starts Gmap4
Displays the Google aerial
Displays an overlay showing land owned by the feds
Is centered at the coordinates Wingman supplied at post 150 on page 6 (46 48.101 -108 53.285).
http://www.mappingsupport.com/p/gma...name=Meridians&layers=0,4,13&transparent=true
Use the sliding control near the upper left corner of the map and zoom in all the way. Next, click the scale symbol near the lower right corner of the map to change from meters to feet.
Assuming the data is 100 accurate (and of course we know it is not) this encroachment appears to be a bit less than 15 feet.
This online map is not a survey. The federal boundaries on the map come from GIS data hosted on a server. If we had actual survey data to work with, no doubt these boundary lines would shift either a little or a lot. (For those of you that are GIS savvy, Gmap4 can display ESRI MapServer tiles and similar tile data available via WMS.)
If you zoom the map out, you will see different colors of federal land. The map legend explaining the different colors is part of the following link. You will need to scroll down to #24.
Map legend:
http://wildfire.cr.usgs.gov/arcgis/rest/services/geomac_dyn/MapServer/legend
2. Has anyone asked BLM for their data?
Post 254 (page 11) says BLM did “ground visits using a survey-grade GPS” and “no encroachment was found”.
That statement means BLM has survey-grade latitude longitude coordinates for (A) one or more points along the new fencing and roads and (B) nearby section corners and quarter corners. BLM absolutely needs both sets of data in order to conclude there is no encroachment.
How many locations did BLM check?
Did they check the spots that are most likely encroachments?
If anyone can obtain that data from BLM, then you could put that data into a file and display it with Gmap4. You could also put that data in a GPX file, load it into your GPS and visit those areas the next time you fly in to any of these BLM parcels that the BLM visited.
If BLM refuses to provide the data in response to a polite request, then you could ask again via a FOIA request. Here is the president’s executive order on open data and the followup memo from OMB:
Executive order:
http://www.whitehouse.gov/the-press...-and-machine-readable-new-default-government-
OMB memo:
http://www.whitehouse.gov/sites/default/files/omb/memoranda/2013/m-13-13.pdf
BTW, the official surveys conducted by BLM (and its predecessor GLO) are online at
http://www.glorecords.blm.gov/search/default.aspx?searchTabIndex=0&searchByTypeIndex=1
I check T12N R22E (includes Wingman’s coordinate in section 13) but there was no useful data.
3. Easy ways to improve consumer grade GPS accuracy
I am completely baffled why almost no useful information is written on this subject. (Listen up you outdoor writers.) Since I tell my clients how to find survey stakes with their GPS, I had to learn how to get the best accuracy from a consumer GPS. I researched that topic and concluded that the three most important factors are:
* Time of day
* WAAS lock
* GLONASS
Time of day. There are websites that predict the times during a day when there will be good and bad satellite constellations. Do your GPS work during the times when the satellites are in a good constellation. You get better accuracy for free.
WAAS lock. If your GPS (a) cannot maintain a lock on a WAAS satellite and (b) does not support GLONASS, then your accuracy is about 50 feet. You can easily lose lock on the WAAS satellite serving your area in heavy forest or if that satellite is blocked by high terrain. The WAAS satellites are stationary and the correction data they provide loses usefulness rather quickly.
GLONASS. This term refers to the Russian GPS satellites. Some GPSs can get data from both the USA and Russian satellites. More data = better accuracy even when you lose lock on the WAAS satellite that covers your area. If you are considering buying a GPS, I recommend that you get one that supports GLONASS.
Here is a list of the Garmin GPSs that support GLONASS:
https://support.garmin.com/support/searchSupport/case.faces?caseId={a3bcf150-1fa1-11e1-73d0-000000000000}
BTW, the iPhone 4s and later support GLONASS as do many android phones.
And here is a pdf file I wrote that has some more information and details on how anyone can get the best accuracy possible from their GPS.
http://www.propertylinemaps.com/p/pdf_tips_for_using_a_gps.pdf
Whew! Sorry for the long post but hopefully this info will prove to be useful. And if anyone would like to know more about Gmap4, the homepage has a FAQ, examples, quick start info (on the Help page), my contact info and more to quickly get you up to speed.
Gmap4 default map:
http://www.mappingsupport.com/p/gmap4.php
Gmap4 homepage:
http://www.mappingsupport.com/p/gmap4.html
Joseph, the Gmap4 guy
Redmond, WA