ported radosts SRTM altitude tool

core/models/survex.py

@@ -1,3 +1,4 @@
+import math 
 import os
 import re
 from urllib.parse import urljoin
@@ -6,7 +7,7 @@ from pathlib import Path
 from django.conf import settings
 from django.db import models
 from django.urls import reverse
-
+from troggle.core.utils import height_from_utm
 
 # from troggle.core.models.troggle import DataIssue # circular import. Hmm
 
@@ -72,7 +73,23 @@ class SurvexStation(models.Model):
         return utmToLatLng(33, self.x, self.y, northernHemisphere=True)[0]
     def long(self):
         return utmToLatLng(33, self.x, self.y, northernHemisphere=True)[1]
-import math
+        
+    def srtm_alt(self):
+        return height_from_utm(self.x, self.y) # height, distance from reference point
+ 
+    def srtm_diff(self):
+        alt, ref = height_from_utm(self.x, self.y) # height, distance from reference point
+        
+        diff = alt - self.z
+        if diff >= 0:
+            diff_str = f"<span style='color:blue'>+{diff:.0f}</span>"
+        else:
+            diff_str = f"<span style='color:red'>{diff:.0f}</span>"
+       
+        return diff_str, ref
+ 
+        
+    
 
 def utmToLatLng(zone, easting, northing, northernHemisphere=True): # move this to utils.py ?
     if not northernHemisphere: