Fastest way to map lakes

rjeeves33rjeeves33 Global Mapper UserPosts: 3
edited November 2014 in Raster Data
Good afternoon

I'm currently using global map version 15. My needs are very simple. Currently I use the software to create an outline of a lake

To perform this I load world map data onto one of my layers then use the "create new area feature tool" .


This works pretty well but some of the big lakes are taking hundreds, if not thousands of mouse clicks to trace around the perimeter. I am wondering is there a way to do the equivalent of a photo shop magic wand that would select all pixels that are blue (my lake) then convert this selection into a vector shape/feature.

Ultimately I export the vector shape/feature into lowrance format for using on my GPS navigator. My current process works perfectly I am just wondering if there is a quicker way to convert the raster mapped into vector.

Thank you very much

Comments

  • PShoreyPShorey Global Mapper Developer Posts: 195Moderator, Trusted User
    edited October 2014
    Hi rjeeves,

    This may help depending on your image:
    1) Open up the Overlay Control Center
    2) Right click on your raster image layer
    3) Select "Create Area Features from Equal Values"

    You should use the Area Bounds to restrict the area to process, and you will need to experiment with the match distance setting a bit. The "Only Create Areas for Selected Colors" setting can help if the lake area is more or less the same color. If you mouse over your lake area, you will see the RGB values on the left side of the status bar. You will probably need to use the digitizer tool to clean the result up a bit. Not quite a one step process, but it will probably get you close to where you want to go.
  • rjeeves33rjeeves33 Global Mapper User Posts: 3
    edited November 2014
    Hi and thank you for your response. I seem to be running into trouble however when I attempt to create area feature from equal values I received the following message


    "None of the selected layers that intersect the specified bounds can have equal value areas created. If any are online layers try first exporting to a local file then low that back in and create equal value areas from that"

    It sounds as though the online rastor image needs exporting then reimported but I am unsure how to do this.

    I did try file > export raster image format > GeoTiff but this claimed to take two days despite me setting the bounds to what was loaded on the screen so I must be doing something wrong.
  • bobwillsbobwills Global Mapper User Posts: 48Trusted User
    edited November 2014
    Hi,

    I am doing a similar project in Ireland and whilst I don't have a specific answer for you I can explain my workflow to see if it helps you.

    Firstly, with regard to your GeoTiff export, it does not necessarily help if you set the bounds to the screen if the screen is zoomed out over a very large area. When you do your GeoTiff export pay attention to the section marked "Sample Spacing/Scale" - I set this to 2.0 meters for my first cut so I can make a reasonably accurate tracing of the lakes/rivers as a starting point. This means your download is a lot quicker, and produces smaller files. You may need to experiment to find a value that better suits your area.

    As we collect more survey data I then do further image downloads of the specific area surveyed at full resolution (export scale) to allow me to improve the accuracy of the shoreline and other objects I want to digitise. I usually create a new shape (more accurate section of shoreline) and merge that shape with the existing shoreline shape - You can just remove or move a few vertices points from the original shoreline if required to eliminate any area that bleeds over the land further than required.

    I find that the colours in the lake/shorelines rarely give an accurate enough shape for me to start with using the "Create Area Features from Equal Values" feature but I must admit I didn't spend a huge amount of time experimenting with it.

    Hope this helps,

    Brian.
  • rjeeves33rjeeves33 Global Mapper User Posts: 3
    edited November 2014
    Hi
    Thank you very much to everyone who has responded. Lots of great information here and I have been playing around with different ways of achieving my goal. I will post what I have found even though it now no longer involves global mapper. This information may be useful to other people trying to make a quick outline of a lake to use on their lowerance plotter

    • Browse to https://www.openstreetmap.org/
    • Set the screen to encompass the entire lake you wish to create a map of
    • Click that export button (if open street site and advises the area is too large you can click the overpass API button to grab the entire screen as a single file)
    • Rename the downloaded file so it includes the file extension .OSM
    • download and install insight mapped Creator (this is a free product) https://insightstore.navico.com/site/insight_charts/7?type=NL-MC-DL&subcategory_id=27&prod_id=522
    • open insight map Creator and set the following options
      • View Menu > processing modes > vector
      • advanced options > Atlas options > Atlas version 10
    • now click add files > browse to the.OSM file you downloaded from the open street map website
    • click the build button

    that should be all that needs to be done. Inside insight map creator application folder there should be a subfolder called BoundAT5s. Inside that folder will be the 3 AT5 files. These are the files that you need to place in the root of your lowrance SD card
    It is possible to export multiple lakes into separate.OSM files. I have been panning around my local area exporting all of the lakes that I may potentially visit and saving each one as a separate OSM file. I then add all of these OSM files into that insight map creator software and it elegantly produces three AT5 files containing all lakes ready to be placed on my SD card
    During the testing phase I have been using the Lowrance Elite-5 simulator which can be downloaded for free from ftp://software.lowrance.com/emulators/Elite5_demo.zip
    this will save a lot of time when you are testing the creation of your maps. You will need to drop the 3 * AT5 files into the following path C:\Program Files (x86)\Navico\Elite-5\Maps0
    if you are running a 32-bit version of Windows then the path should be C:\Program Files\Navico\Elite-5\Maps0
    When you open the simulator remember to move to the location where the lake or feature you are looking for resides :-)

    Hope this helps someone
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