Merge pull request #6 from scottstanie/geoid-speedup

Geoid speedup
scottstanie · Aug 11, 2022 · 07e5a58 · 07e5a58
2 parents e3053f5 + 95f67b2
commit 07e5a58
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Showing 2 changed files with 17 additions and 52 deletions.
diff --git a/sardem/conversions.py b/sardem/conversions.py
@@ -3,17 +3,13 @@
 import shutil
 import subprocess
 
-import requests
-
 from . import utils
 
 logger = logging.getLogger("sardem")
 
-URL_EGM08 = "http://download.osgeo.org/proj/vdatum/egm08_25/egm08_25.gtx"
-URL_EGM96 = "http://download.osgeo.org/proj/vdatum/egm96_15/egm96_15.gtx"
-EGM_URLS = {
-    "egm96": URL_EGM96,
-    "egm08": URL_EGM08,
+EPSG_CODES = {
+    "egm96": "5773",  # https://epsg.io/5773
+    "egm08": "3855",  # https://epsg.io/3855
 }
 EGM_FILES = {
     "egm96": os.path.join(utils.get_cache_dir(), "egm96_15.gtx"),
@@ -22,23 +18,25 @@
 
 
 def egm_to_wgs84(filename, output=None, overwrite=True, copy_rsc=True, geoid="egm96"):
-    """Convert a DEM with a EGM96 vertical datum to WGS84 heights above ellipsoid"""
+    """Convert a DEM with a EGM96/2008 vertical datum to WGS84 heights above ellipsoid"""
 
     if output is None:
         ext = os.path.splitext(filename)[1]
         output = filename.replace(ext, ".wgs84" + ext)
 
-    egm_file = EGM_FILES[geoid]
-    if not os.path.exists(egm_file):
-        download_egm_grid(geoid=geoid)
+    code = EPSG_CODES[geoid]
+    # Source srs: WGS84 ellipsoidal horizontal, EGM geoid vertical
+    s_srs = '"epsg:4326+{}"'.format(code)
+    # Target srs: WGS84 horizontal/vertical
+    t_srs = '"epsg:4326"'
 
     # Note: https://gdal.org/programs/gdalwarp.html#cmdoption-gdalwarp-tr
     # If not specified, gdalwarp will generate an output raster with xsize=ysize
     # We want it to match the input file
     xsize, ysize = _get_size(filename)
     cmd = (
-        'gdalwarp {overwrite} -s_srs "+proj=longlat +datum=WGS84 +no_defs +geoidgrids={egm_file}" '
-        '-t_srs "+proj=longlat +datum=WGS84 +no_defs" -of ENVI -ts {xsize} {ysize} '
+        'gdalwarp {overwrite} -s_srs {s_srs} -t_srs {t_srs}'
+        ' -of ENVI -ts {xsize} {ysize} '
         ' -multi -wo NUM_THREADS=4 -wm 4000 {inp} {out}'
     )
     cmd = cmd.format(
@@ -47,7 +45,8 @@ def egm_to_wgs84(filename, output=None, overwrite=True, copy_rsc=True, geoid="eg
         overwrite="-overwrite" if overwrite else "",
         xsize=xsize,
         ysize=ysize,
-        egm_file=egm_file,
+        s_srs=s_srs,
+        t_srs=t_srs,
     )
     logger.info(cmd)
     subprocess.run(cmd, check=True, shell=True)
@@ -103,32 +102,3 @@ def convert_dem_to_wgs84(dem_filename, geoid="egm96", using_gdal_bounds=False):
     if not using_gdal_bounds:
         # Now shift back to the .rsc is pointing to the middle of the pixel
         utils.shift_rsc_file(rsc_filename, to_gdal=False)
-
-
-def download_egm_grid(geoid="egm96"):
-    if geoid == "egm96":
-        url = URL_EGM96
-    elif geoid in ("egm08", "egm2008"):
-        url = URL_EGM08
-    else:
-        raise ValueError("Unknown geoid: {}".format(geoid))
-
-    egm_file = EGM_FILES[geoid]
-    if os.path.exists(egm_file):
-        logger.info("{} already exists, skipping.".format(egm_file))
-        return
-
-    size = _get_file_size_mb(url)
-    logger.info(
-        "Performing 1-time download {} ({:.0f} MB file), saving to {}".format(
-            url, size, egm_file
-        )
-    )
-    with open(egm_file, "wb") as f:
-        resp = requests.get(url)
-        f.write(resp.content)
-
-
-def _get_file_size_mb(url):
-    # https://stackoverflow.com/a/44299915/4174466
-    return int(requests.get(url, stream=True).headers["Content-length"]) / 1e6
diff --git a/sardem/cop_dem.py b/sardem/cop_dem.py
@@ -1,5 +1,4 @@
 import logging
-import os
 from copy import deepcopy
 
 import requests
@@ -9,7 +8,6 @@
 TILE_LIST_URL = "https://copernicus-dem-30m.s3.amazonaws.com/tileList.txt"
 URL_TEMPLATE = "https://copernicus-dem-30m.s3.amazonaws.com/{t}/{t}.tif"
 DEFAULT_RES = 1 / 3600
-
 logger = logging.getLogger("sardem")
 utils.set_logger_handler(logger)
 
@@ -29,7 +27,6 @@ def download_and_stitch(
     from osgeo import gdal
 
     gdal.UseExceptions()
-    geoid = "egm08"
     # TODO: does downloading make it run any faster?
     # if download_vrt:
     #     cache_dir = utils.get_cache_dir()
@@ -38,16 +35,13 @@ def download_and_stitch(
     #         make_cop_vrt(vrt_filename)
     # else:
     vrt_filename = "/vsicurl/https://raw.githubusercontent.com/scottstanie/sardem/master/sardem/data/cop_global.vrt"  # noqa
-    egm_file = conversions.EGM_FILES[geoid]
-    if not os.path.exists(egm_file):
-        conversions.download_egm_grid(geoid=geoid)
 
     if keep_egm:
         t_srs = s_srs = None
     else:
-        s_srs = "+proj=longlat +datum=WGS84 +no_defs +geoidgrids={}".format(egm_file)
-        t_srs = "+proj=longlat +datum=WGS84 +no_defs"
-
+        code = conversions.EPSG_CODES["egm08"]
+        s_srs = '"epsg:4326+{}"'.format(code)
+        t_srs = '"epsg:4326"'
     xres = DEFAULT_RES / xrate
     yres = DEFAULT_RES / yrate
 
@@ -68,6 +62,7 @@ def download_and_stitch(
 
     # Used the __RETURN_OPTION_LIST__ to get the list of options for debugging
     logger.info("Creating {}".format(output_name))
+    logger.info("Fetching remote tiles...")
     cmd = _gdal_cmd_from_options(vrt_filename, output_name, option_dict)
     logger.info("Running GDAL command:")
     option_dict["callback"] = gdal.TermProgress