Hi everyone - as this is my first post to MI-L I should apologize for the imminent ramble.
I have several years experience warping raster historic maps (pre 1936 OS plus other individual surveys) for use in various GIS, converting their map projections to the current British National Grid. Having started in MapInfo and for the reasons outlined by Jaromir found it was not achievable, so as an alternative I used ER Mapper to georeference and warp the raster images for use in MapInfo. Having moved employer I was again required to carry out the same tasks in ArcView, and used a very good (and possibly free?) extension called Imagewarp to georeference custom historic map tiles. You can then composed an image mosaic of the historic map in ER Mapper. I would recommend this as the easiest method in my experience as you can revisit the mosaic as and when you get time to add new tiles to it, and all the georeferencing is carried out in one application (ArcView). Obviously there are many different capable software applications capable of this kind of operation - some GIS and other Image Processing packages. Whether warping images for use in MapInfo or ArcView, ER Mapper has the advantage that if you are working with large maps (one I am thinking of was a double A0 size, hand painted original from 1829AD) and have a smallish scanner you can still scan tiles and georeference them separately, ensuring relatively good registration accuracy per tile, then you can seamlessly mosaic these images together, drawing a clipping polygon on each tile to remove edge matching problems with null pixels overlying adjoining tiles, and then write a compressed .ecw file out for use in either MapInfo or ArcView. Its a pretty complex multi step process but if you need any help or advice please feel free to email me off list. At a MUG UK demo of Vertical Mapper recently I raised the question as to whether orthorectification and rubber sheeting might be added to VM as a future development, as it is the logical Raster extension to MapInfo. In my opinion that added functionality would really extend the tools available to exclusive MapInfo users, and it seems that having acquired Vertical Mapper that MapInfo are in the perfect position to enhance this product. /ramble OFF Greg Phillips -------------------------------------------------------------- Greg Phillips BA PGDip MIFA Environment GIS Consultant Built and Natural Environment Northamptonshire County Council PO Box 163 County Hall Northampton NN1 1AX Tel: 01604 237433 Mob: 07799 832584 -------------------------------------------------------------- >>> Jaromir Svasta <[EMAIL PROTECTED]> 10/29/03 06:13am >>> MapInfo only adjusts the coordinate system of vector layers to fit the raster. It applies one transformation formula (I think bilinear) all over the area, so if the raster is distorted it cannot guarantee that control points will match the raster, doesn't matter how many of them there are. You need to rubber-sheet the raster. MapInfo won't help you :-( Arc Info, Grass and some other "heavy" GIS can make it. Jaromir On Tue, 28 Oct 2003 23:50:35 +0100, Joep Orbons <[EMAIL PROTECTED]> wrote: > Dear readers, > > I process historical maps and fit them to todays topography. The problem > with these historical maps is the distortion of the maps. This > distortion is not regular in X and/or Y direction, it can be very much > rotated and scaled different in seperate parts of the maps. > These maps always have some points I recognize and that I can mark on > todays topography. Sometimes many points, sometimes only a few. > How can I un-distort these maps, scanned or digitised, to fit the known > points? I don't think it is possible in MapInfo. Maybe I need a seperate > program with two layers: One layer with todays topography and known > points and a second layer with the scan. Then drag points of the scan to > the modern topography where the rest of the map follows. The more > points, the more accurate. > Any suggestions? > > Thanks, > > Joep Orbons > Souterrains: [EMAIL PROTECTED]
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