' Description: Creates a hillshade grid from a converted DEM source in decimal degrees
' by calculating an appropriate Zfactor
' 
' Name:  Spatial.DEMShade
' 
' Requires:  Spatial Analyst Extension
' 
' Self:  
' 
' Returns:  
' 
' FileName:  demshad.ave


theView = av.GetActiveDoc

' CREATE HILLSHADE FOR ACTIVE GTHEME
'
t = theView.GetActiveThemes.Get(0)

' OBTAIN PARAMETERS FOR HILLSHADE
'
status = TRUE
while (status)
  paramList = MsgBox.MultiInput("Input parameters for hillshade:","Compute Hillshade",{"Azimuth (0 - 360):","Altitude (0 - 90):"},{"315","45"})

  if (paramList.Count <2)
  then
   return NIL
  end
  theAzimuth = paramList.Get(0)
  theAltitude = paramList.Get(1)
  if (theAzimuth.IsNumber and ((theAzimuth.AsNumber >= 0) and (theAzimuth.AsNumber <= 360)))
  then
    azOK = TRUE
  else
    azOK = FALSE
    MsgBox.Info("Azimuth must be a number from 0 to 360","Compute Hillshade")
  end
  if (theAltitude.IsNumber and ((theAltitude.AsNumber >= 0) and (theAltitude.AsNumber <=
  90))) then
    alOK = TRUE
  else

    alOK = FALSE
    MsgBox.Info("Altitude must be a number from 0 to 90","Compute Hillshade")
  end
  if (azOK and alOK) then
    status = FALSE
  else
    status = TRUE
  end
end

' OBTAIN GRID FROM THEME AND CREATE HILLSHADE
'
g = t.GetGrid
'r = g.HillShade(theAzimuth.AsNumber,theAltitude.AsNumber,NIL)
'zFactor = ( 1 / length of degree of long ) * 3600
theRec  = t.ReturnExtent
theLatitudeBottom  = theRec.GetBottom.Abs
theLatitudeTop = theRec.GetTop.Abs

if (theLatitudeTop > theLatitudeBottom) then
  theDiff = theLatitudeTop - theLatitudeBottom
  theHalfDiff = theDiff / 2
  theLatitude = theLatitudeTop - theHalfDiff
else
  theDiff = theLatitudeBottom - theLatitudeTop
  theHalfDiff = theDiff / 2
  theLatitude = theLatitudeTop + theHalfDiff
end

' USE .abs TO MAKE SURE THE Z FACTOR IS A POSITIVE VALUE
' THE MULTIPLIER (3600 / 360) CAN BE ADJUSTED TO INCREASE OR DECREASE THE
' Z FACTOR WHICH WILL CHANGE THE LENGTH OF SHADOWS
zFactor = ( 1 / (6370997*(theLatitude.Cos)*(Number.GetPi/180))) * (3600 / 360)
msgbox.info(zfactor.abs.AsString,"Z factor")
r = g.HillShade(theAzimuth.AsNumber,theAltitude.AsNumber,zFactor.abs)

' RENAME DATA SET
'
aFN = av.GetProject.GetWorkDir.MakeTmp("hlshd", "")
r.Rename(aFN)

' ERROR CHECK
'
if (r.HasError) then return NIL end

' CREATE A THEME
'
gthm = GTheme.Make(r)  

' CREATE APPROPRIATE LEGEND FOR THEME
'
theLegend = gthm.GetLegend
theLegend.Area(gthm,"Value",9)
theSymbolList = theLegend.GetSymbols
theNullSymbol = theSymbolList.Get(theSymbolList.Count - 1)
theSymbolList.Remove(theSymbolList.Count - 1)
theSymbolList.RampColors(Color.GetBlack,Color.GetWhite)

theSymbolList.Add(theNullSymbol)
gthm.UpdateLegend

' SET NAME OF THEME
'
gthm.SetName("Hillshade of " + t.GetName)

' ADD THEME TO THE SPECIFIED VIEW
'
theView.AddTheme(gthm)