GCPs Setup Procedure

Ground Control Points or well Know GCPs  are a precise position measurement made on the ground, typically using a high precision Global Navigation Satellite Systems GNSS or Terrestrial Positition Systems TPS. GCPs points are useful for correcting distortions in datasets and georeferencing the data to predifined state or country coordinate systems. Ground Control Points can be set as a static or temporary. Usually its recommended to paint taget at pavement , sidewalks or concrete with hight color contrast. 

Supported Photogrammetric Target

Drone Touchup Service Support:

  • T, V and L shape Ground Control Point
  • Cross (+) shape Gr0und Control Point
  • General well defined figure 
  • Comercial or Costum target shape
GCP File

GCP file format its simple:

  • The first line should contain the name of the projection
  • Subsequent lines are the X, Y & Z coordinates, your associated pixels, the image filename and optional extra fields, separated by tabs or spaces
  • Elevation values can be set to “NaN” to indicate no value or NULL
  • The 7th column (optional) typically contains the label or GCP code
  • If you submit file named gcp_list.txt, Drone Touchup will automatically detect it
  • GCP file with customized name can be specified using at process edit task options –gcp <path>
  • If you have a gcp file and want to georeference with exif instead, then you can specify at process edit task options –use-exif
  • If you have high precision GPS measurements in your images (RTK) and want to use that information along with a gcp file, you can specify at process edit task options  –force-gps
Recommendations
  • No bushes or trees around 10 meters
  • 0-3% terrain slope site (5 meters sorroundings)
  • Need to be visible from a monimun of 6 overlapped images
  • Minimun of 5 GCPs per datasets
  • Located at hight and low elevations
  • Geometrically well distributed as 5 of domino
  • 5 Minutues RTK Oberservations
  • Network or Cell Adjustment RTK Network Correction
  • Single baseline RTK correction 10 min  within 20 km baseline + 10 additional minutes every 5 km 
Region Coordinate Systems
  • Dominican Republic UTM84-19n
  • +proj=utm +zone=19 +north +ellps=WGS84 +datum=WGS84 +units=m +no_defs
  • Puerto Rico Virgin Island (PRVI NAd83 5200)
  • +proj=pipeline +step +inv +proj=lcc +lat_0=17.8333333333333 +lon_0=-66.4333333333333 +lat_1=18.4333333333333 +lat_2=18.0333333333333 +x_0=200000 +y_0=200000 +ellps=GRS80 +step +proj=hgridshift +grids=pvhpgn.gsb +step +proj=lcc +lat_0=17.8333333333333 +lon_0=-66.4333333333333 +lat_1=18.4333333333333 +lat_2=18.0333333333333 +x_0=200000 +y_0=200000 +ellps=GRS80

Steps for Georeference Image Datasets

Our company has more than 8 years of experience perfomring  photogrammetric missions in the Caribbean Area. That is why we are the professional team best prepared to offer this type of service. We have served clients in the architecture industry, urban and rural development, engineering and construction, energy, mining, environmental preservation, among others. If you need a successful results and cost effective alternative contact us for a quote and schedule of works requested.