Live and recent posts from across the Fediverse tagged #surveying, aggregated by home.social.
Ground control took absolute accuracy from metres down to centimetres. The price: a few hours of fieldwork to survey the targets, and fifteen to twenty-five minutes of tagging them in the office.
So the only question that matters is what the map is for. A canopy index does not need it. A lawyer does.
The rule of thumb: a map's error should be a tenth of the thing you want to measure.
For a five metre stockpile, fifty centimetres of error is fine. For a crack in a wall, fifty centimetres is a disaster. The error number tells you whether the map is fit for the job.
Seven surveyed targets. Four become ground control, and the software fits the map to them exactly. Three are held back as checkpoints, and the software never sees them.
Compare the finished map against those three and the gap is the honest error of the whole survey. Three is the minimum. Five is better.
For most mapping, canopy work and change detection, relative accuracy is enough.
But when a map will be read by a surveyor, a client or a lawyer, it needs ground control. Without it every pixel can sit two to five metres from where it really is, and the processing report cannot tell you which way.
Awesome video by Daniel Steiner about the origin of the famous Swiss topo maps. 🇨🇭🗺️
Also he’s very lucky that because of his excellent geography videos, this latest video was in collaboration with the Swiss government. (I definitely recommend subscribing to his channel.)
#maps #cartography #Mapstodon #surveying #gischat #DanielSteiner #Swisstopo #Switzerland #Swiss
Mapping Global GNSS Vertical Velocities To Solid Earth Figure Change
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https://doi.org/10.1029/2026JB034224 <-- shared paper
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https://www.labrujulaverde.com/en/2026/09/earth-isnt-a-perfect-sphere-but-its-changing-shape-faster-than-expected/ <-- shared technical article
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H/T @gregory Helmer | Professional Land Surveyor, Geospatial Engineer
“[This paper] describes analysis of GNSS data showing the Earth's equator-to-pole radius difference is shrinking by ~1.8 mm/yr where previous glacial isostatic adjustment models accounted for ~0.3 mm/yr. This increasing change in the solid Earth with mass redistribution has the opposite effect on the geoid. The solid Earth is getting rounder while the geoid is becoming more oblate…”
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“... PLAIN LANGUAGE SUMMARY: This study looks at how the shape of our planet is slowly changing over time. Earth is not a perfect sphere – it is slightly flattened at the poles and bulging at the equator. But this shape isn't fixed; it evolves due to natural processes like melting ice, shifting land, and changes in the Earth's surface and interior. To better understand these changes, we used satellite-based measurements of how the Earth's surface moves up or down in different places. We developed a method to analyze this data and track whether Earth is becoming more or less flattened over time. Our results indicate an acceleration of polar uplift accompanied by a comparably increasing rate of equatorial subsidence. This means that solid Earth's overall shape is becoming slightly less flattened. We further find that this geometric change is not fully mirrored in the Earth's gravity field, indicating that the geometric response of the solid Earth and the gravity field response to mass-redistribution do not evolve identically. These findings are important because they help scientists understand how the planet responds to melting glaciers and shifting water. This kind of knowledge is essential for tracking climate change and its impact on Earth's long-term behavior…”
#Geodesy #GNSS #Geophysics #Geoid #oblate #SolidEarth #GlacialIsostaticAdjustment #MassRedistribution #Geospatial #Geomatics #Surveying #RemoteSensing #SatelliteData#EarthScience #Geoscience #ClimateChange #GIS #spatial #mapping #spatialanalysis #global #datum #datums #solidearth #rounder #change #isostatic #isostaticadjustmentmodel #massredistribution