[pdal] Z value change on reprojection in pdal 1.6
Michael Smith
michael.smith.erdc at gmail.com
Tue Nov 14 07:06:33 PST 2017
Hmm, it might be that pdal is reading the source vertical projection as navd88 and if you are reprojecting and not specifying a vertical projection, it might be assuming wgs84. You can try specifying the output projection as epsg:5070+5703
Mike
--
Michael Smith
Remote Sensing/GIS Center
US Army Corps of Engineers
From: Doug Newcomb <newcomb.ttg at gmail.com>
Date: Tuesday, November 14, 2017 at 9:58 AM
To: Michael Smith <michael.smith.erdc at gmail.com>
Cc: pdal <pdal at lists.osgeo.org>
Subject: Re: [pdal] Z value change on reprojection in pdal 1.6
Micheal,
The problem is the z values of all of the point values are have been changed. I had created a raster from the mean value of the ground points from the pdal reprojected data. I then went back to NOAA's site and selected a small subset to compare and had their engine deliver the points in Albers Meters Conus NAVD88. I imported the points to create a raster in the same way and then subtraced the Z value of the pdal reprojected points from the NOAA reprojected points. The height values vary by 32-36 m ( see below) .
That was why I was asking if I had missed a step that ensured that the Z values stayed at the Geoid12A/12B/NAVD88 values.
Tue Nov 14 09:45:55 2017)
r.info map=noaa_pdal_vert_diff_m at dnewcomb
+----------------------------------------------------------------------------+
| Map: noaa_pdal_vert_diff_m at dnewcom Date: Tue Nov 14 09:36:19 2017 |
| Mapset: dnewcomb Login of Creator: dnewcomb |
| Location: seva_albers |
| DataBase: /data2/grass70_data |
| Title: noaa_pdal_vert_diff_m |
| Timestamp: none |
|----------------------------------------------------------------------------|
| |
| Type of Map: raster Number of Categories: 0 |
| Data Type: FCELL |
| Rows: 12465 |
| Columns: 20411 |
| Total Cells: 254423115 |
| Projection: NAD83 / Conus Albers |
| N: 1687158.47979 S: 1668162.01936 Res: 1.52398399 |
| E: 1653024.11274 W: 1621917.96408 Res: 1.52398945 |
| Range of data: min = 32.17395 max = 36.06071 |
| |
| Data Description: |
| generated by r.mapcalc |
| |
| Comments: |
| 2635_mean_ground_1_524_test_from_noaa_meters at dnewcomb - |
| 2635_mean_ground_1_524 at PERMANENT |
| |
+----------------------------------------------------------------------------+
Doug
On Mon, Nov 13, 2017 at 8:20 PM, Michael Smith <michael.smith.erdc at gmail.com> wrote:
Doug,
It looks like perhaps the header metadata is not correct, which is what I think you are seeing from lasinfo. When you inspected the Decimal Degrees file it shows
"bbox":
{
"maxx": -76.2527221,
"maxy": 37.9068695,
"maxz": -5.777103023,
"minx": -76.2571767,
"miny": 37.9028129,
"minz": -35.71281856
},
which match your albers output.
--
Michael Smith
Remote Sensing/GIS Center
US Army Corps of Engineers
From: pdal <pdal-bounces at lists.osgeo.org> on behalf of Doug Newcomb <newcomb.ttg at gmail.com>
Date: Monday, November 13, 2017 at 8:14 PM
To: pdal <pdal at lists.osgeo.org>
Subject: [pdal] Z value change on reprojection in pdal 1.6
Ok,
Finally diving into pdal more deeply. I installed the docker instance of pdal 1.6 and tried a bit of command line reprojection:
I downloaded some data from the NOAA website and re-projected from Decimal Degrees to Albers Meters Conus ( EPSG:5070)
pdal translate /data/20100503_LAS_S23_1836_10.laz /data/albers_20100503_LAS_S23_1836_10.laz -f filters.reprojection --filters.reprojection.out_srs="EPSG:5070"
For the input data , lasinfo gives :
Minimum and Maximum Attributes (min,max)
---------------------------------------------------------
Min X, Y, Z: -76.2571767, 37.9028129, 0.024
Max X, Y, Z: -76.2527221, 37.9068695, 29.966
Bounding Box: -76.2571767, 37.9028129, -76.2527221, 37.9068695
for the output laz file, lasinfo gives:
Minimum and Maximum Attributes (min,max)
---------------------------------------------------------
Min X, Y, Z: 1707096.44, 1829911.69, -35.72
Max X, Y, Z: 1707557.20, 1830350.12, -5.77
Bounding Box: 1707096.44, 1829911.69, 1707557.20, 1830350.12
pdal info for the input file gives:
{
"filename": "\/data\/20100503_LAS_S23_1836_10.laz",
"pdal_version": "1.6.0 (git-version: 94ad83)",
"stats":
{
"bbox":
{
"EPSG:4326":
{
"bbox":
{
"maxx": -76.2527221,
"maxy": 37.9068695,
"maxz": -5.777103023,
"minx": -76.2571767,
"miny": 37.9028129,
"minz": -35.71281856
},
"boundary": {
"coordinates" : [
[
[ -76.257176700000002, 37.902812900000001 ],
[ -76.257176700000002, 37.906869499999999 ],
[ -76.2527221, 37.906869499999999 ],
[ -76.2527221, 37.902812900000001 ],
[ -76.257176700000002, 37.902812900000001 ]
]
],
"type" : "Polygon"
}
},
"native":
{
"bbox":
{
"maxx": -76.2527221,
"maxy": 37.9068695,
"maxz": 29.966,
"minx": -76.2571767,
"miny": 37.9028129,
"minz": 0.024
},
"boundary": {
pdal info on the output laz file gives:
{
"filename": "\/data\/albers_20100503_LAS_S23_1836_10.laz",
"pdal_version": "1.6.0 (git-version: 94ad83)",
"stats":
{
"bbox":
{
"EPSG:4326":
{
"bbox":
{
"maxx": -76.25185156,
"maxy": 37.90686951,
"maxz": -5.77,
"minx": -76.25806657,
"miny": 37.9021939,
"minz": -35.72
},
"boundary": {
"coordinates" : [
[
[ -76.258066569999997, 37.903041880000004 ],
[ -76.257028300000002, 37.90686951 ],
[ -76.251851560000006, 37.90602148 ],
[ -76.252890100000002, 37.9021939 ],
[ -76.258066569999997, 37.903041880000004 ]
]
],
"type" : "Polygon"
}
},
"native":
{
"bbox":
{
"maxx": 1707557.2,
"maxy": 1830350.12,
"maxz": -5.77,
"minx": 1707096.44,
"miny": 1829911.69,
"minz": -35.72
},
"boundary": {
Am I missing a switch in the translate command?
Doug
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