dhoenig


Does anyone know how to convert ESRI Shape File X.Y coords to Lat,Lon I would like to plot these on VE but I need the formula to convert the point to lat/lon. Thanks!




Re: ESRI Shape Files

Sean McLeod


ShapeFiles don't use a fixed projection, the X,Y coordinates are floating point values that could be used for any projection or even to store geographic lat/lon coordinates for that matter.

So if your ShapeFile has lat/lon values then there is no conversion needed, otherwise you need to know what projection your coordinates are in and then perform a reverse projection from that to geographic lat/lon.

Cheers






Re: ESRI Shape Files

Duncan Garratt

ESRI to Virtual Earth

One smart way is to use MsSqlSpatial that has an ESRI shape file import utility into MS SQL 2005. When you have imported the shape file you will need to convert the coordinates to Lat/long, which can be done using GPS Tools from Franson in Sweden, which are highly accurate grid coordinate conversions. Then simply query your database and plot your points, polylines etc on a VE Map in the normal way. If you are looking to use transparent images as overlays, then use SharpMap in conjunction MsSqlSpatial. It sounds a bit complicated to start with but is well worth the effort.

Duncan Garratt

http://www.gis-logic.co.uk

Franson Link

http://www.franson.com

MsSqlSpatial Link

http://www.codeplex.com/MsSqlSpatial/

SharpMap Link

http://www.codeplex.com/Wiki/View.aspx ProjectName=SharpMap

Please note that MsSqlSpatial is for MS SQL 2005 plus and not MS SQL 2000.

MsSqlSpatial Features

  • OGC Simple Features Specification for SQL Revision 1.1 conformant (non official but verifiable).
  • 2D Geometries supported: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, GeometryCollection.
  • Predicate functions: Equals, Disjoint, Intersects, Touches, Crosses, Within, Contains, Overlaps, Covers, CoveredBy, Relate, IsWithinDistance.
  • Spatial analysis functions: ConvexHull, Intersection, Union, Difference, SymDifference.
  • Linear referencing functions: LineInterpolatePoint, LineLocatePoint, LineSubstring.
  • Spatial relationship and processing functions: Distance, Length, Area, Buffer, Centroid, PointOnSurface, Simplify, Polygonize, LineMerge and many more.
  • Coordinate systems aware: SRID, SetSRID, Transform.
  • Spatial indexing: Simple but effective implementation using table-valued functions (FilterQuery, JoinFilterQuery, IsWithinDistanceQuery, RelateQuery)
  • Aggregate functions that overcome the 8000 bytes limitation of normal user-defined aggregate functions: UnionAggregate, EnvelopeAggregate, IntersectionAggregate.
  • GML support: AsGML function.
  • Import from shapefiles and PostGIS tables.

Future:

  • Export to shapefiles and PostGIS tables.
  • AsSVG function.
  • Support as data source by SharpMap rendering engine (already available in its latest source code package).







Re: ESRI Shape Files

Vuduchile66

As an alternative way to get your data out of the shapefile is to use a couple of extraction and conversion utilities. A shapefile viewer [1] can export your shapefile data into a spreadsheet (CSV), then use the CorpsCon utility [2] to convert your XY data into Lat Lon. You will need to know your projection though. If you don't you'll waste too much time trying the different projection options.


Points in the ocean are no good!!

[1] - Shapefile Viewer
http://www.qarah.com/shapeviewer/

[2] - Army Corps of Engineers - CorpsCon
http://crunch.tec.army.mil/software/corpscon/corpscon.html