Category: Géo-traitements

dataset :

photos with timestamps

UBX from M2 and from base station

Processing:

1- Post-Process base station and get corrected coordinates

2- with Emlid Studio (or RTKLib) calculate events (triggers) positions from UBX

as output one gets an …._events.pos file that gives corrected coordinates for each event together with a timestamp

3- extract timestamps from exif of pictures

use exiftool with this command

exiftool -n -csv -filemodifydate -api TimeZone=UTC *.JPG > metadata.csv

the output file “metadata.csv” gives the name of the picture and the timestamp in UTC format

4- Merge …_events.pos and pictures events

For now I’ve got this ugly Python script:

#! /usr/bin/env python

"""
Update Emlid Reach Survey points with PPK position output from RTKLIB
David Shean
dshean@gmail.com
Edited to fix Pandas datetime/Timestamp tz issues, and a few key changes likely based on Emlid updates
"""

import os
import argparse
import numpy as np
import pandas as pd

def getparser():
    parser = argparse.ArgumentParser(description='Update Emlid Reach Survey points with \
            PPK positions from RTKLIB')
    parser.add_argument('survey_pts_csv_fn', type=str, help='Survey point csv filename')
    parser.add_argument('ppk_pos_fn', type=str, help='PPK pos filename')
    return parser


def main():
    parser = getparser()
    args = parser.parse_args()

    survey_pts_csv_fn = args.survey_pts_csv_fn
    ppk_pos_fn = args.ppk_pos_fn

    print('Loading: %s' % survey_pts_csv_fn)
    survey_pts = pd.read_csv(survey_pts_csv_fn, parse_dates=[1], header=0)
    survey_pts['date']=pd.to_datetime(survey_pts['FileModifyDate'],format="%Y:%m:%d %H:%M:%S+00:00")
    survey_pts.sort_values('date', inplace=True)
    survey_pts.index=survey_pts['date']
    print(survey_pts.dtypes)
    print(survey_pts)
    header = 'Date UTC latitude(deg) longitude(deg)  height(m)   Q  ns   sdn(m)   sde(m)   sdu(m)  sdne(m)  sdeu(m)  sdun(m) age(s)  ratio'
    print('Loading: %s' % ppk_pos_fn)
    ppk_pos = pd.read_csv(ppk_pos_fn, comment='%', delim_whitespace=True, names=header.split(), parse_dates=[[0,1]])
    ppk_pos['date']=pd.to_datetime(ppk_pos['Date_UTC'])
    ppk_pos.index=ppk_pos['Date_UTC']
    print(ppk_pos.dtypes)
    print(ppk_pos)

    # Applying merge_asof on data and store it
    # in a variable
    merged_dataframe = pd.merge_asof(ppk_pos, survey_pts, right_index=True,left_index=True,direction='nearest',tolerance=pd.Timedelta("1s"))

    print(merged_dataframe)

    #Write out new file
    out_fn = os.path.splitext(survey_pts_csv_fn)[0]+'_merged.csv'
    print("Writing out: %s" % out_fn)
    merged_dataframe.to_csv(out_fn)    

if __name__ == "__main__":
    main()

5- In Metashape, import the coordinates of the cameras from the new file