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Messages - Jelf

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Map Making Support / Re: Help with land ownership maps
« on: November 18, 2015, 03:57:53 PM »
Be cautious when using parcel data from a county or state website.  A lot of that data was produced by simply digitizing old hand drawn ‘assessor maps’.  Those maps were never meant to accurately depict parcel lines.

As part of my job I often am comparing the shape of a property as shown by GIS parcel lines to the shape of the same property as shown by a survey.  Yes, sometimes the GIS parcel lines do a good job of showing the correct shape.  This is most often true in urban and suburban areas where the parcels are smaller and often multiple parcels have the same  basic size and shape.

The biggest differences I see are in more rural areas where each parcel is a different shape and parcel lines go every which way.

Of course if there is any difference in the shape of a property as shown on a survey map and the shape as shown by GIS data, the survey is correct.


In states that are part of the PLSS (most states west of the Mississippi and some states east of that river) it is common for legal descriptions to be expressed like the example given by the OP:
SE1/4 NW 1/4.

Such legal descriptions do not have vectors.

To further complicate matters, sections are often not perfect squares and section 1/4 corners are often *not* at the midpoint between section corners.

If your county has an online GIS you might be able to get approximate coordinates.  Be careful - sometimes those coordinates are in "state plane" and not latitude longitude.  Also, sometimes the property lines on a county GIS are fairly good in one area and obviously wrong in other areas. 

In addition to looking at the thread Boyd mentioned, try thinking of a google search.  Maybe something like: coordinates for property corners

Using The Maps/Garmin Software / Re: Alternative software to Basecamp?
« on: August 27, 2014, 03:26:05 AM »
But the main thing I want is the ability to view the waypoint and track data recorded on my GPS on top of a topo map that also shows trails.

If you save the data recorded by your GPS as a GPX file, then you can display that file on high resolution USGS topo maps using Gmap4.  I am the developer of that browser app.

You do have to put your GPX file online.  However Google Sites provides free hosting and the Gmap4 documentation has step-by-step instructions for using Google Sites.

For example, the following link shows the GPX file I recorded for a hike in Washington State:

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

I am the developer of Gmap4 which is an enhanced Google map viewer that is free for non-commercial use.  You can use it to display your GPX files on the highest resolution seamless topographic map that is available anywhere online.  These hi-res topos cover the USA (except maybe Alaska).

Disclosure:  If you poke around on the Gmap4 homepage or on any Gmap4 map, you may see a link to http://www.PropertyLineMaps.com.  That is a commercial service that I run.  You do not need to be a client of that commercial service in order to use Gmap4.  I intend to keep Gmap4 free (for non-commercial use) and without ads or banners as part of my way to "pay it forward".

Here is an example of Gmap4 displaying a GPX track from a hike I did in the Cascade Mountains near Seattle.

When you open a Gmap4 link with a mobile browser on a smartphone or tablet, then it automatically displays a touch-friendly interface.  A mouse interface is automatically displayed on desktops/laptops.

To display your own GPX file with Gmap4:
1.  Put your GPX (or KML, KMZ, TPO) file online.
2.  Edit the q parameter in the above link so it points at your file instead of pointing at my file.
3.  Paste the revised link into your browser.

Google Sites provides free file hosting and you can find step-by-step instructions by searching the Gmap4 Help file on "google sites".  The Gmap4 homepage (see below) has a link to the Help file.

Tip: Do not use any spaces in your file name.  Use the underline character instead.

If you are in Canada, you can display your GPX files on vector topos, like so:

If you are not in the USA or Canada, then a good basemap to use is the OSM Cycle map which includes topographic lines and crowd-sourced trails.  The following map is centered on a spot in the Italian Alps.

When you are making a link to display a GPX file (or other supported file type), then the only *required* parameter is ‘q’.  If you make a Gmap4 link that does not include the ‘q’ parameter, then the default basemap (t=t1, Google terrain) will be displayed.

To specify a basemap to display when the map opens, include the ‘t’ parameter:
To see the allowable values for the ‘t’ parameter, please search the Gmap4 Help file on ‘t8’ and then scroll up just a bit to see the full list.

NOTE! If you are using Gmap4 to display GPX (or TPO) files, then it is very important that you read about the  ‘refresh’ parameter in the Help file.

Here are a few things you can do after the map opens:
* Double click.  Center the map at the spot clicked.
* Right click.  Display coordinates in various forms and get draggable directions.
* Menu ==> Link to this map.  Get a link that will reproduce the map you see on your screen.
* Menu ==> My location.  Uses the GPS in your mobile device to center the map at your location.
* Menu ==> Search.  Includes searching on UTM coordinates.
* Menu ==> Draw and save.  Trip planning with GPX output.  One click can make both a waypoint and routepoint.
* Menu ==> Hill shading.  Variable hill shading for the “t4 Topo High” basemap.
* Menu ==> UTM - LatLng - Off.  Display UTM grid.
* Menu ==> Declination.  Get the current magnetic declination for the center of the map.

Some forums allow Gmap4 maps to be embedded as ‘live’ maps in the body of forum posts.   For example, scroll down a bit on this trip report for a ‘live’ map.

And if you are savvy about GIS, then you can display your GPX file on top of any data that is available from GIS servers via either the REST interface or WMS interface.  Here are a few examples of Gmap4 displaying data from GIS servers:

The Gmap4 homepage has a FAQ, examples, quick start info (in the Help file) 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

General Discussion / Re: Alternatives to Basecamp or Mapquest
« on: August 11, 2013, 04:46:14 AM »
If you try Gmap4 please note that printing through your browser works best with Firefox.

Joseph, the Gmap4 guy

It looks to me that EveryTrail uses a zoom setting and map center such that all of the track fits on the lefthand part of the map while leaving room for the slideshow on top of the righthand part of the map.   I do not see any way to change that behavior.

If you try Gmap4 as Dave suggests you can use the free Google Sites to put your pics online.

Joseph, the Gmap4 guy

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