Translating between AutoCAD drawing points and geographic locations using .NET Part 3

I hadn’t planned on writing a third part to this series, but then Mads Paulin – who I mentioned in the last post – got back to me with some information that’s really worth sharing.

I’d pinged Mads while looking for a way to list the available coordinate systems to the user (another question from Coralie Jacobi, who had originally kicked off the series). I’d found out that the coordinate system definitions are primarily stored in this folder…

C:\ProgramData\Autodesk\Geospatial Coordinate Systems 14.01

… but I hadn’t worked out to extract any information from the contained CSD files.

Mads delivered the goods: he explained there’s a GeoCoordinateSystem class that contains a static method CreateAll(). The returned array of GeoCoordinateSystem classes can then be iterated, accessing the information you want from each one.

There’s also a static Create() method which lets you instantiate a single GeoCoordinateSystem class based on the XML you retrieve from the GeoLocation object. So we can now rip out our previous DynamicXML implementation (I’m glad we went through it, though: it’s still an interesting technique for people needing to retrieve data from XML). Mads will be happy: as the architect for the feature he was temporarily embarrassed by the hoops I ended up jumping through to get at this simple bit of information. :-)

Here’s the updated C# code. Look in particular for the new LCS (ListCoordinateSystems) command and the greatly simplified PrintCoordinateSystem() helper function. (The LLPF and PFLL commands should work just as they did, last time around, of course.)

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Runtime;
using System;
 
namespace GeoLocationAPI
{
  public class Commands
  {
    [CommandMethod("IGR")]
    public void InsertGeoRef()
    {
      var doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null)
        return;
      var ed = doc.Editor;
      var db = doc.Database;
      var msId = SymbolUtilityServices.GetBlockModelSpaceId(db);
 
      if (HasGeoData(db))
      {
        // Report and return: could also open the object for
        // write and modify its properties, of course
 
        ed.WriteMessage("\nDrawing already has geo-location data!");
        return;
      }
 
      // Let's create some geolocation data for this drawing,
      // using a handy method to add it to the modelspace
      // (it gets added to the extension dictionary)
 
      var data = new GeoLocationData();
      data.BlockTableRecordId = msId;
      data.PostToDb();
 
      // We're going to define our geolocation in terms of
      // latitude/longitude using the Mercator projection
      // http://en.wikipedia.org/wiki/Mercator_projection
 
      data.CoordinateSystem = "WORLD-MERCATOR";
      data.TypeOfCoordinates = TypeOfCoordinates.CoordinateTypeGrid;
 
      // Use the lat-long for La Tene, my local "beach"
      // (it's on a lake, after all :-)      
 
      var geoPt = new Point3d(7.019438, 47.005247, 0);
 
      // Transform from a geographic to a modelspace point
      // and add the information to our geolocation data
 
      var wcsPt = data.TransformFromLonLatAlt(geoPt);
      data.DesignPoint = wcsPt;
      data.ReferencePoint = geoPt;
 
      // Let's launch the GEOMAP command to show our geographic
      // overlay
 
      ed.Command("_.GEOMAP", "_AERIAL");
 
      // Now we'll add a circle around our location
      // and that will provide the extents for our zoom
 
      using (var tr = db.TransactionManager.StartTransaction())
      {
        var ms =
          tr.GetObject(msId, OpenMode.ForWrite) as BlockTableRecord;
        if (ms != null)
        {
          // Add a red circle of 7K units radius
          // centred on our point
 
          var circle = new Circle(wcsPt, Vector3d.ZAxis, 7000);
          circle.ColorIndex = 1;
          ms.AppendEntity(circle);
          tr.AddNewlyCreatedDBObject(circle, true);
        }
        tr.Commit();
      }
 
      // And we'll zoom to the circle's extents
 
      ed.Command("_.ZOOM", "_OBJECT", "_L", "");
    }
 
    [CommandMethod("CGI")]
    public void CreateGeoMapImage()
    {
      var doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null)
        return;
      var ed = doc.Editor;
      var db = doc.Database;
 
      // Get the first corner of our area to convert to a
      // GeomapImage
 
      var ppo = new PromptPointOptions("\nSpecify first corner");
      var ppr = ed.GetPoint(ppo);
      if (ppr.Status != PromptStatus.OK)
        return;
 
      var first = ppr.Value;
 
      // And get the second point as a corner (to rubber-band
      // the selection)
 
      var pco =
        new PromptCornerOptions("\nSpecify second corner", first);
      ppr = ed.GetCorner(pco);
 
      if (ppr.Status != PromptStatus.OK)
        return;
 
      var second = ppr.Value;
 
      // We'll use an event handler on the Database to check for
      // GeomapImage entities being added
      // (we'll use a lambda but assigned to a variable to be
      // able to remove it, afterwards)
 
      ObjectId giId = ObjectId.Null;
      ObjectEventHandler handler =
        (s, e) =>
        {
          if (e.DBObject is GeomapImage)
          {
            giId = e.DBObject.ObjectId;
          }
        };
 
      // Simply call the GEOMAPIMAGE command with the two points
 
      db.ObjectAppended += handler;
      ed.Command("_.GEOMAPIMAGE", first, second);
      db.ObjectAppended -= handler;
 
      // Only continue if we've collected a valid ObjectId
 
      if (giId == ObjectId.Null)
        return;
 
      // Open the entity and change some values
 
      try
      {
        using (var tr = doc.TransactionManager.StartTransaction())
        {
          // Get each object and check if it's a GeomapImage
 
          var gi =
            tr.GetObject(giId, OpenMode.ForWrite) as GeomapImage;
          if (gi != null)
          {
            // Let's adjust the brightmess/contrast/fade of the
            // GeomapImage
 
            gi.Brightness = 90;
            gi.Contrast = 40;
            gi.Fade = 20;
 
            // And make sure it's at the right resolution and
            // shows both aerial and road information
 
            gi.Resolution = GeomapResolution.Optimal;
            gi.MapType = GeomapType.Hybrid;
 
            gi.UpdateMapImage(true);
          }
 
          tr.Commit();
        }
      }
      catch (Autodesk.AutoCAD.Runtime.Exception)
      {
        ed.WriteMessage(
          "\nUnable to update geomap image entity." +
          "\nPlease check your internet connectivity and call " +
          "GEOMAPIMAGEUPDATE."
        );
      }
    }
 
    [CommandMethod("LCS")]
    public void ListCoordinateSystems()
    {
      var doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null)
        return;
      var ed = doc.Editor;
 
      // 
      var css = GeoCoordinateSystem.CreateAll();
 
      ed.WriteMessage("\nAvailable coordinate systems:\n");
 
      int i=1;
      foreach (var cs in css)
      {
        ed.WriteMessage("\n{0} {1}", i, cs.ID);
        ++i;
      }
    }
 
    [CommandMethod("LLFP")]
    public void LatLongFromPoint()
    {
      var doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null)
        return;
      var ed = doc.Editor;
      var db = doc.Database;
 
      if (!HasGeoData(db))
      {
        ed.WriteMessage(
          "\nCurrent drawing has no geo-location information."
        );
        return;
      }
 
      // Get the drawing point to be translated into a lat-lon
 
      var ppo = new PromptPointOptions("\nSpecify point");
      var ppr = ed.GetPoint(ppo);
      if (ppr.Status != PromptStatus.OK)
        return;
 
      var dwgPt = ppr.Value;
 
      // Translate the drawing point to a lat-lon
 
      var res = TranslateGeoPoint(db, dwgPt, true);
 
      // Print any coordinate system information
 
      PrintCoordinateSystem(ed, res.Item2);
 
      // And then the point itself
 
      var lonlat = res.Item1;
      ed.WriteMessage(
        "\nLatitude-longitude is {0},{1}", lonlat.Y, lonlat.X
      );
    }
 
    [CommandMethod("PFLL")]
    public void PointFromLatLong()
    {
      var doc = Application.DocumentManager.MdiActiveDocument;
      if (doc == null)
        return;
      var ed = doc.Editor;
      var db = doc.Database;
 
      if (!HasGeoData(db))
      {
        ed.WriteMessage(
          "\nCurrent drawing has no geo-location information."
        );
        return;
      }
 
      // Get the latitude and longitude to be translated
      // to a drawing point
 
      var pdo = new PromptDoubleOptions("\nEnter latitude");
      var pdr = ed.GetDouble(pdo);
      if (pdr.Status != PromptStatus.OK)
        return;
 
      var lat = pdr.Value;
 
      pdo.Message = "\nEnter longitude";
      pdr = ed.GetDouble(pdo);
      if (pdr.Status != PromptStatus.OK)
        return;
 
      var lon = pdr.Value;
 
      var lonlat = new Point3d(lon, lat, 0.0);
 
      // Translate the lat-lon to a drawing point
 
      var res = TranslateGeoPoint(db, lonlat, false);
 
      // Print any coordinate system information
 
      ed.WriteMessage(res.Item2);
 
      PrintCoordinateSystem(ed, res.Item2);
 
      // And then the point itself
 
      var dwgPt = res.Item1;
      ed.WriteMessage(
        "\nDrawing point is {0},{1},{2}", dwgPt.X, dwgPt.Y, dwgPt.Z
      );
    }
 
    private static void PrintCoordinateSystem(Editor ed, string xml)
    {
      var gcs = GeoCoordinateSystem.Create(xml);
      ed.WriteMessage("\nCoordinate system: {0}", gcs.ID);
    }
 
    private Tuple<Point3d, string> TranslateGeoPoint(
      Database db, Point3d inPt, bool fromDwg
    )
    {
      using (
        var tr = db.TransactionManager.StartOpenCloseTransaction()
      )
      {
        // Get the drawing's GeoLocation object
 
        var gd =
          tr.GetObject(db.GeoDataObject, OpenMode.ForRead)
            as GeoLocationData;
 
        // Get the output point...
        // dwg2lonlat if fromDwg is true,
        // lonlat2dwg otherwise
 
        var outPt =
          (fromDwg ?
            gd.TransformToLonLatAlt(inPt) :
            gd.TransformFromLonLatAlt(inPt)
          );
 
        var cs = gd.CoordinateSystem;
 
        tr.Commit();
 
        return new Tuple<Point3d, string>(outPt, cs);
      }
    }
 
    private static bool HasGeoData(Database db)
    {
      // Check whether the drawing already has geolocation data
 
      bool hasGeoData = false;
      try
      {
        var gdId = db.GeoDataObject;
        hasGeoData = true;
      }
      catch { }
      return hasGeoData;
    }
  }
}

When we run the LCS command, we actually see the tail end of a looong list of coordinate systems:

WGS72be/b.UTM-16N
WGS72be/b.UTM-16S
WGS72be/b.UTM-17N
WGS72be/b.UTM-17S
WGS72be/b.UTM-18N
WGS72be/b.UTM-18S
WGS72be/b.UTM-19N
WGS72be/b.UTM-19S
WGS72be/b.UTM-1N
WGS72be/b.UTM-1S
WGS72be/b.UTM-20N
WGS72be/b.UTM-20S
WGS72be/b.UTM-21N
WGS72be/b.UTM-21S
WGS72be/b.UTM-22N
WGS72be/b.UTM-22S
WGS72be/b.UTM-23N
WGS72be/b.UTM-23S
WGS72be/b.UTM-24N
WGS72be/b.UTM-24S
WGS72be/b.UTM-25N
WGS72be/b.UTM-25S
WGS72be/b.UTM-26N
WGS72be/b.UTM-26S
WGS72be/b.UTM-27N
WGS72be/b.UTM-27S
WGS72be/b.UTM-28N
WGS72be/b.UTM-28S
WGS72be/b.UTM-29N
WGS72be/b.UTM-29S
WGS72be/b.UTM-2N
WGS72be/b.UTM-2S
WGS72be/b.UTM-30N
WGS72be/b.UTM-30S
WGS72be/b.UTM-31N
WGS72be/b.UTM-31S
WGS72be/b.UTM-32N
WGS72be/b.UTM-32S
WGS72be/b.UTM-33N
WGS72be/b.UTM-33S
WGS72be/b.UTM-34N
WGS72be/b.UTM-34S
WGS72be/b.UTM-35N
WGS72be/b.UTM-35S
WGS72be/b.UTM-36N
WGS72be/b.UTM-36S
WGS72be/b.UTM-37N
WGS72be/b.UTM-37S
WGS72be/b.UTM-38N
WGS72be/b.UTM-38S
WGS72be/b.UTM-39N
WGS72be/b.UTM-39S
WGS72be/b.UTM-3N
WGS72be/b.UTM-3S
WGS72be/b.UTM-40N
WGS72be/b.UTM-40S
WGS72be/b.UTM-41N
WGS72be/b.UTM-41S
WGS72be/b.UTM-42N
WGS72be/b.UTM-42S
WGS72be/b.UTM-43N
WGS72be/b.UTM-43S
WGS72be/b.UTM-44N
WGS72be/b.UTM-44S
WGS72be/b.UTM-45N
WGS72be/b.UTM-45S
WGS72be/b.UTM-46N
WGS72be/b.UTM-46S
WGS72be/b.UTM-47N
WGS72be/b.UTM-47S
WGS72be/b.UTM-48N
WGS72be/b.UTM-48S
WGS72be/b.UTM-49N
WGS72be/b.UTM-49S
WGS72be/b.UTM-4N
WGS72be/b.UTM-4S
WGS72be/b.UTM-50N
WGS72be/b.UTM-50S
WGS72be/b.UTM-51N
WGS72be/b.UTM-51S
WGS72be/b.UTM-52N
WGS72be/b.UTM-52S
WGS72be/b.UTM-53N
WGS72be/b.UTM-53S
WGS72be/b.UTM-54N
WGS72be/b.UTM-54S
WGS72be/b.UTM-55N
WGS72be/b.UTM-55S
WGS72be/b.UTM-56N
WGS72be/b.UTM-56S
WGS72be/b.UTM-57N
WGS72be/b.UTM-57S
WGS72be/b.UTM-58N
WGS72be/b.UTM-58S
WGS72be/b.UTM-59N
WGS72be/b.UTM-59S
WGS72be/b.UTM-5N
WGS72be/b.UTM-5S
WGS72be/b.UTM-60N
WGS72be/b.UTM-60S
WGS72be/b.UTM-6N
WGS72be/b.UTM-6S
WGS72be/b.UTM-7N
WGS72be/b.UTM-7S
WGS72be/b.UTM-8N
WGS72be/b.UTM-8S
WGS72be/b.UTM-9N
WGS72be/b.UTM-9S
WGS84.AusAntarctic/LM
WGS84.BLM-14NF
WGS84.BLM-15NF
WGS84.BLM-16NF
WGS84.BLM-17NF
WGS84.CanLam.3
WGS84.CRTM05
WGS84.PlateCarree
WGS84.PseudoMercator
WGS84.SCAR-SP19-20
WGS84.SCAR-SP21-22
WGS84.SCAR-SP23-24
WGS84.SCAR-SQ01-02
WGS84.SCAR-SQ19-20
WGS84.SCAR-SQ21-22
WGS84.SCAR-SQ37-38
WGS84.SCAR-SQ39-40
WGS84.SCAR-SQ41-42
WGS84.SCAR-SQ43-44
WGS84.SCAR-SQ45-46
WGS84.SCAR-SQ47-48
WGS84.SCAR-SQ49-50
WGS84.SCAR-SQ51-52
WGS84.SCAR-SQ53-54
WGS84.SCAR-SQ55-56
WGS84.SCAR-SQ57-58
WGS84.SCAR-SR13-14
WGS84.SCAR-SR15-16
WGS84.SCAR-SR17-18
WGS84.SCAR-SR19-20
WGS84.SCAR-SR27-28
WGS84.SCAR-SR29-30
WGS84.SCAR-SR31-32
WGS84.SCAR-SR33-34
WGS84.SCAR-SR35-36
WGS84.SCAR-SR37-38
WGS84.SCAR-SR39-40
WGS84.SCAR-SR41-42
WGS84.SCAR-SR43-44
WGS84.SCAR-SR45-46
WGS84.SCAR-SR47-48
WGS84.SCAR-SR49-50
WGS84.SCAR-SR51-52
WGS84.SCAR-SR53-54
WGS84.SCAR-SR55-56
WGS84.SCAR-SR57-58
WGS84.SCAR-SR59-60
WGS84.SCAR-SS04-06
WGS84.SCAR-SS07-09
WGS84.SCAR-SS10-12
WGS84.SCAR-SS13-15
WGS84.SCAR-SS16-18
WGS84.SCAR-SS19-21
WGS84.SCAR-SS25-27
WGS84.SCAR-SS28-30
WGS84.SCAR-SS31-33
WGS84.SCAR-SS34-36
WGS84.SCAR-SS37-39
WGS84.SCAR-SS40-42
WGS84.SCAR-SS43-45
WGS84.SCAR-SS46-48
WGS84.SCAR-SS49-51
WGS84.SCAR-SS52-54
WGS84.SCAR-SS55-57
WGS84.SCAR-SS58-60
WGS84.SCAR-ST01-04
WGS84.SCAR-ST05-08
WGS84.SCAR-ST09-12
WGS84.SCAR-ST13-16
WGS84.SCAR-ST17-20
WGS84.SCAR-ST21-24
WGS84.SCAR-ST25-28
WGS84.SCAR-ST29-32
WGS84.SCAR-ST33-36
WGS84.SCAR-ST37-40
WGS84.SCAR-ST41-44
WGS84.SCAR-ST45-48
WGS84.SCAR-ST49-52
WGS84.SCAR-ST53-56
WGS84.SCAR-ST57-60
WGS84.TM-116SE
WGS84.TM-132SE
WGS84.TM-36SE
WGS84.TM-6NE
WGS84.UPSNorth
WGS84.UPSSouth
WGS84.USGS-AntarticMtn
WGS84.Winkel
WI-C
WI-N
WI-S
WI27-TM
WI83-C
WI83-CF
WI83-N
WI83-NF
WI83-S
WI83-SF
WI83-TM
WIHP-C
WIHP-CF
WIHP-N
WIHP-NF
WIHP-S
WIHP-SF
WilkinMN-F
WilkinMN-IF
WilkinMN-M
WinnebagoWI-F
WinnebagoWI-IF
WinnebagoWI-M
WinonaMN-F
WinonaMN-IF
WinonaMN-M
WisconsinTM-HP
WoodWI-F
WoodWI-IF
WoodWI-M
WORLD-EQDIST-CYL
WORLD-LL
WORLD-LM-CONIC
WORLD-LM-TAN
WORLD-MERCATOR
WORLD-MILLER
WORLD-ROBINSON
WORLD-SINUSOIDAL
WORLD-VDGRNTN
WrightMN-F
WrightMN-IF
WrightMN-M
WSIG
WV-N
WV-S
WV83-N
WV83-NF
WV83-S
WV83-SF
WVHP-N
WVHP-NF
WVHP-S
WVHP-SF
WY-E
WY-EC
WY-W
WY-WC
WY83-E
WY83-EC
WY83-ECF
WY83-EF
WY83-W
WY83-WC
WY83-WCF
WY83-WF
WYHP-E
WYHP-EC
WYHP-ECF
WYHP-EF
WYHP-W
WYHP-WC
WYHP-WCF
WYHP-WF
Xian80.GK-13
Xian80.GK-14
Xian80.GK-15
Xian80.GK-16
Xian80.GK-17
Xian80.GK-18
Xian80.GK-19
Xian80.GK-20
Xian80.GK-21
Xian80.GK-22
Xian80.GK-23
Xian80.GK/CM-105E
Xian80.GK/CM-111E
Xian80.GK/CM-117E
Xian80.GK/CM-123E
Xian80.GK/CM-129E
Xian80.GK/CM-135E
Xian80.GK/CM-75E
Xian80.GK/CM-81E
Xian80.GK/CM-87E
Xian80.GK/CM-93E
Xian80.GK/CM-99E
Xian80.GK3d-25
Xian80.GK3d-26
Xian80.GK3d-27
Xian80.GK3d-28
Xian80.GK3d-29
Xian80.GK3d-30
Xian80.GK3d-31
Xian80.GK3d-32
Xian80.GK3d-33
Xian80.GK3d-34
Xian80.GK3d-35
Xian80.GK3d-36
Xian80.GK3d-37
Xian80.GK3d-38
Xian80.GK3d-39
Xian80.GK3d-40
Xian80.GK3d-41
Xian80.GK3d-42
Xian80.GK3d-43
Xian80.GK3d-44
Xian80.GK3d-45
Xian80.GK3d/CM-102E
Xian80.GK3d/CM-105E
Xian80.GK3d/CM-108E
Xian80.GK3d/CM-111E
Xian80.GK3d/CM-114E
Xian80.GK3d/CM-117E
Xian80.GK3d/CM-120E
Xian80.GK3d/CM-123E
Xian80.GK3d/CM-126E
Xian80.GK3d/CM-129E
Xian80.GK3d/CM-132E
Xian80.GK3d/CM-135E
Xian80.GK3d/CM-75E
Xian80.GK3d/CM-78E
Xian80.GK3d/CM-81E
Xian80.GK3d/CM-84E
Xian80.GK3d/CM-87E
Xian80.GK3d/CM-90E
Xian80.GK3d/CM-93E
Xian80.GK3d/CM-96E
Xian80.GK3d/CM-99E
Xian80.LL
XY-BC
XY-BL
XY-BR
XY-CA
XY-CC
XY-CF
XY-CG
XY-CL
XY-CM
XY-DAM
XY-DK
XY-DM
XY-FT
XY-FU
XY-GC
XY-GL
XY-GM
XY-HM
XY-IFT
XY-IIN
XY-IMI
XY-IN
XY-IYD
XY-KM
XY-KT
XY-M
XY-MI
XY-ML
XY-MM
XY-NM
XY-PE
XY-PO
XY-RD
XY-RO
XY-SC
XY-SL
XY-SY
XY-UI
XY-YD
Yacare.LL
Yacare/E.LL
YAP
YellowMedicineMN-F
YellowMedicineMN-IF
YellowMedicineMN-M
YEM-E
YEM-GK7
YEM-GK8
YEM-GK9
YEM-U37
YEM-U38
YEM-U39
YEM-W
Yemen96.UTM-38N
Yemen96.UTM-39N
YemenNtl96.LL
ZAIRE
Zanderij.LL
Zanderij.SurinameTM
Zanderij.SurinameTMOld
Zanderij.TM-54NW
Zanderij.UTM-21N
ZIM-35
ZIM-35/01
ZIM-36
ZIM-36/01

So we can see we have 6845 available to us (many more than the list shown inside AutoCAD 2015). I’m not sure how best they’d be filtered or categorised – this isn’t my specialist field, of course – but if someone has a request/suggestion for how to do so, please do post a comment. A lot more can clearly be done with this list than just printing the ID of each entry.

Update:

Mads tells me the library we use contains more coordinate systems than AutoCAD supports: AutoCAD only currently works with “projected” coordinate systems (the others in the list are used by other Autodesk products). You can modify the LCS command to filter the list by wrapping the contents of its foreach loop in an if statement, e.g.:

if (cs.Type == GeoCSType.Projected)
{
  ed.WriteMessage("\n{0} {1}", i, cs.ID);
  ++i;
}

That reduces the list down to 6132 coordinate systems that can be used by AutoCAD. Which should still be plenty, I would think. Thanks, Mads!

Through the Interface

A blog for developers programming with Autodesk platforms, particularly AutoCAD and APS. With a special focus on AR/VR and IoT.

September 08, 2014

Translating between AutoCAD drawing points and geographic locations using .NET – Part 3

Kean Walmsley

Search

Categories

Recent Posts

Archives

Autodesk Blogs