Starting a Raster image GPS.. ideas?

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  1. #1
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    Starting a Raster image GPS.. ideas?

    Hi Guys,
    Although I write in C, this is more of an English question.

    I wrote a vector based GPS mapping program that works nicely
    It would be nice to use satellitte imagery underneath the topographic
    vector data.
    I've done a vector GPS on two platforms now, but never thought about
    an image based GPS before.

    Basically, I'd like an English description of how this works.
    How the image tiles are referenced for example, are hi-res images
    resized when zooming out? (this one will have map tile images stored offline).
    Are the image tiles referenced with coordinates?

    I do already have a lot of information, like the geographic coordinates
    of each corner, and centre of the screen for whatever zoom level
    or map position you are viewing, and what the value of a single
    pixel is relating to incrementing a decimal lat/long value, rotation
    angle, and basically any variables that you'd know by having a GPS
    mapper already working.

    Any ideas appreciated!
    Art.

  2. #2
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    Do you mean like Google street view?
    Fact - Beethoven wrote his first symphony in C

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    No, just top down 2D view with rotation.

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    Top down 2D view - Like Google Maps?
    Fact - Beethoven wrote his first symphony in C

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    Start by getting a geo-referenced map? (they are basically maps with a few coordinate/pixel location pairs)

    Tiling would be the hard part I'm imagining.

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    Quote Originally Posted by cyberfish View Post
    Start by getting a geo-referenced map? (they are basically maps with a few coordinate/pixel location pairs)

    Tiling would be the hard part I'm imagining.
    Already taken care of. $500 AU for licence the map I want to use for distribution in a program,
    and I know the precise map boundaries.
    I think handling zoom will be difficult, since images are to be stored off line,
    and I'd prefer to scale down existing imagery, than store a bunch of different zoom levels.

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    I think the biggest problem with that is processing speed (and hence your program's responsiveness).

    If the tiles are too big, when they take a lot of time to decode when you are zoomed in. If the tiles are too small, you'll need to read thousands of files to render just one screen when zoomed out.

    That's why all tiles-based GPS programs I know store tiles at many different zoom levels. Unless they don't expect the user to zoom much.

  8. #8
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    Unfortunately I do expect the user to zoom much
    It's $500AU to licence the imagery for what is to be a free program, but I'm going ahead.

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