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Importing a map in spherical Mercator projection

Maps from sites can be easily imported into Multiplans, as they all share the same spherical Mercator projection (which bears number 10 in Multiplans).

Tutorial: importing a map from Google maps

In this tutorial, we will import this google map of Majorca into Multiplans.
map of Majorca Island

Before following the tutorial, we recommend to read page Import a map to have a general overview on importing maps.
The map above can be imported in the following steps:
  1. Enlarge the map window as much as possible (the left white panel can be hidden by clicking on button <<).
  2. Take a screenshot of the map, starting exactly at the upper-left corner of the map to have a picture as the one above.
    On MacOS, this is done by using keystroke command+shift+4 and selecting the appropriate area on the screen.
  3. We need now to georeference the map. Click on button "Link" above the map. A panel pops up with a link to the map:

    Copy the last part of the link which is of the form
    ll=39.645882,2.867432&spn=0.774042,1.29364&t=h&z=10

  4. Using the above numbers, we can calculate easily the information needed to georeference the map for Multiplans.
    The link indicates the longitude (2.867432) and latitude (39.645882) coordinates of the center of the map, the width (1.29364) and the height (0.774042) of the map in degrees, and the zoom level (z=10).
    • The resolution of a google map (in meters/pixel) depends on the zoom level according to the table below
      Zoom level Resolution
      (in m/pixel)
      0 156543.03392
      1 78271.51696
      2 39135.75848
      3 19567.87924
      4 9783.93962
      5 4891.96981
      6 2445.98490
      7 1222.99245
      8 611.49622
      9 305.74811
      10 152.87405
      11 76.43702
      12 38.21851
      13 19.10925
      14 9.55462
      15 4.77731
      16 2.38865
      17 1.19432
      18 0.59716
      19 0.29858
      Note: the above resolutions were found by using formula
      res = π R / (256 * 2^(z-1))
      where π = 3.1415926536, R = 6378137 is the radius of the Earth in meters and z is the zoom level.
    • The longitude and latitude of the upper-left corner of the map can be calculated by using:
      longitude = longitude_center - width / 2
      latitude = latitude_center + height / 2
      • In this example:
      longitude = 2.867432 - 1.29364 / 2 = 2.2206120
      latitude = 39.645882 + 0.774042 / 2 = 40.0330125

    5. Using a plain text editor (TextEdit on Mac or Notepad on Windows), create a referencing file named ref.txt containing the following data:
    File ref.txt
    10
    152.87405
    152.87405
    2.2206120
    40.0330125
    <-- line 1: projection number (10 = spherical Mercator)
    <-- line 2: horizontal resolution (in meters/pixel)
    <-- line 3: vertical resolution (in meters/pixel)
    <-- line 4: longitude of upper-left corner of the map
    <-- line 5: latitude of upper-left corner of the map

  5. Drag your screenshot onto Zoomify Converter to slice the image into tiles. Zoomify Converter quits automatically once the task is completed. A folder containing the map tiles is created next to your map image file (with the same name as your image).
  6. Move file ref.txt file into the folder containing the tiles, and compress this folder into a zip archive.
  7. The map can now be imported into Multiplans !

    Download map: Majorque.zip

Help on importing maps from myTopo.com

To import a map from myTopo.com, we can use link gmap4 to view the map fullscreen (map opens at zoom level 14), and then proceed basically as in the case of google maps. To get the coordinates of the upper-left corner of the map, right-click on the map:
If you encounter problems importing a map from myTopo.com, contact the technical support.


Tip: assembling quickly large maps
If it is allowed by the license of the maps (eg maps of the USGS), one can use the following tips to assemble quickly large maps: