Mapping

[JDL]

Those doing ‘mapping’ for clients, are you using gcp’s? If not, what type of deliverables are construction clients commonly asking for?

 

[dougcjohn]

I believe many use GCP, some associated with RTK / PPK.

In the RTK/PPK and GCP schema, I'm a newby myself, and have been not using GCP although moving in that direction, including wanting to learn & include PPK as well. Been exploring various options in HW and SW to use with my existing platforms.

Currently I do a 2D orthogramatry and a Video loop with 2 autonomous missions: Litchi with I2 and X5S for Video loop, and I2 with X4S for MME or GSP to create map grid. My current projects are 1-2 city block structures and currently get very detailed images they can use to verify or measure. I'm not sure how much GCP's as a image marker would improve the product final image and so far no interst to associate GPS with physical gound point utilizing PPK.

The map grids are added to a MME Location Set do client can click through progression. Images or files are available to Client to use in additional work. The videos are edited a bit and provided to view. These videos will eventually make a time lapse over duration of project.

In addition, I take multiple photos with M2P for Mgmt brief books they present to their clients or post on their web site.

 

[R Martin]

Those doing ‘mapping’ for clients, are you using gcp’s? If not, what type of deliverables are construction clients commonly asking for?

I map and use a Geo 7X with a centimeter mapping package installed as well as AeroPoints for control. All of our contracts require a minimum of six surveyed benchmarks to be set in accordance with USGS specs (outsourced to a local surveyor). We are mainly involved in subsurface utility work but also do before and after as well as job progress (if we must).
If you don't have site control you don't have a map; you can still use the dataset for non-critical measurements but beyond that its basically worthless as far as a mapping product.

 

[Earthman]

GCPs are points (targets) on the ground that are surveyed and visible in the aerial photos. I use white 5-gal bucket lids as GCP targets. I‘ve drilled a hole in the center of the lids so I can pin them to the ground with a large nail and carry them in a stack on a “stringer“ I made. The heads of the nails or holes in the lids are often visible in the photos, which helps us enter coordinates of the GCPs in the photo processing software. We survey the coordinates of the GCPs using RTK GPS or other survey instruments (robotic total station, etc.). You can also use painted GCPs, prominent features that appear in the photos, etc., but you need to survey or know the location of all GCPs. There are also commercially made GCP targets that have RTK GPS receivers built into them but they are expensive and I wonder about their ability to “see” the sky/GPS satellites when sitting on the ground.

GCPs are necessary for best accuracy of an aerial survey because they allow the processing software to correct distortions that may be in the photos/photo mosaic from various sources. An RTK GPS receiver on the aircraft also improves accuracy of the survey by providing better locations of the photographs, but you need GCPs to correct for other errors such as distortions caused by the camera lens, and camera movement and tilt that are too small for the sensors on the aircraft to resolve and record. I use GCPs and no RTK on the aircraft all the time.

 

[dougcjohn]

GCPs are points (targets) on the ground that are surveyed and visible in the aerial photos. I use white 5-gal bucket lids as GCP targets. I‘ve drilled a hole in the center of the lids so I can pin them to the ground with a large nail and carry them in a stack on a “stringer“ I made. The heads of the nails or holes in the lids are often visible in the photos, which helps us enter coordinates of the GCPs in the photo processing software. We survey the coordinates of the GCPs using RTK GPS or other survey instruments (robotic total station, etc.). You can also use painted GCPs, prominent features that appear in the photos, etc., but you need to survey or know the location of all GCPs. There are also commercially made GCP targets that have RTK GPS receivers built into them but they are expensive and I wonder about their ability to “see” the sky/GPS satellites when sitting on the ground.

GCPs are necessary for best accuracy of an aerial survey because they allow the processing software to correct distortions that may be in the photos/photo mosaic from various sources. An RTK GPS receiver on the aircraft also improves accuracy of the survey by providing better locations of the photographs, but you need GCPs to correct for other errors such as distortions caused by the camera lens, and camera movement and tilt that are too small for the sensors on the aircraft to resolve and record. I use GCPs and no RTK on the aircraft all the time.

Your usage of GCP and reasoning is how I've understood it. That rational increases as size of the image increases. It also helps increase the alignment of the images when the GCPs are identified in a several images.

The need to use RTK/PPK and associating images to "true points on the ground" are needed for survey requirements, not for many other tasks using the 2D Ortho map. It remains a helpful, useful map with out GPS pts to earth or GCP. Volumetric, measuring a object, laying a known unit of measurement on ground improves the accuracy; noting location of objects, progression of work, verification of stage completion or verification of design are all obtainable as a useful map... as an image. Creation of 3D model is also obtained and possible from the mapped images.

 

[adm_geomatics]

GCP's of some sort in every map. Yes, there are several methods and centimeter accuracy is not always required nor is GNSS equipment. For the drone no RTK as it is not acceptable for certified mapping without logging, but PPK on all phase grade verifications and asbuilts.

 

[dougcjohn]

GCP's of some sort in every map. Yes, there are several methods and centimeter accuracy is not always required nor is GNSS equipment. No RTK as it is not acceptable for certified mapping without logging, but PPK on all phase grade verifications and asbuilts.

Hope all is good with company & families... noticed the passing of Chaz. He sounded like one heck of a guy!

 

[adm_geomatics]

Hope all is good with company & families... noticed the passing of Chaz. He sounded like one heck of a guy!

Thanks for that. All's well. The funeral was Friday and was a reminder that he surely was one of a kind and brought together a great group of people.

 

[FrankPlatt]

You can use RTK or PPK