SurveyStar LDP Companion

SurveyStar LDP Companion is a field-ready toolkit for surveyors and GIS professionals who design Low Distortion Projections (LDPs) — the custom local coordinate systems that keep grid distances close to ground distances on construction, cadastral, and infrastructure projects. Standard systems like UTM can distort distances by hundreds of parts per million — enough that prefabricated steel or precast structures won't fit together on site. An LDP built for your project area fixes that. This app puts the full workflow in your pocket, fully offline. WHY IT MATTERS A distortion of just 480 ppm — typical for UTM on some projects — is nearly half a metre per kilometre. SurveyStar LDP Companion shows you distortion in both ppm and millimetres per kilometre, so the consequence for your project is never abstract. FOUR TOOLS, ONE WORKFLOW • K0 Calculator Compute the scale factor k₀ from a design latitude and ellipsoid height, using the mean radius of curvature. The starting point for any new LDP. • LDP Builder Build Transverse Mercator, Lambert Conformal Conic (1SP), or Hotine Oblique Mercator definitions with custom central meridian, latitude of origin, false easting/northing, and units (metre, international foot, US survey foot). Instantly get a PROJ string, ESRI WKT1 (.prj), OGC WKT2 (.wkt), and a Trimble JobXML (.jxl) file ready to import into GNSS controllers. • Distortion Analyst Check any LDP against real survey points — one at a time or as a batch CSV import. See combined scale factor, grid convergence, and distortion in ppm and mm/km per point, with a clear pass/fail verdict (mean |distortion| under 20 ppm = ready for construction). Export results to TXT, Markdown, or PDF. • Projection Advisor Import a project boundary (GeoJSON, Shapefile, or GeoPackage) and let the app analyse its shape — major-axis orientation and elongation — to recommend TM, LCC, or Oblique Mercator. Overlay elevation (DEM) and population data to find the best design height and optimise the origin and scale factor for minimum distortion across the whole area, with a Dennis-style distortion table. MY LDP LIBRARY Save every LDP you build to a local database, organised by project/group, with search and sort. Edit, duplicate, back up as JSON, or export straight to a GNSS controller as a Trimble JobXML (.jxl) file — individually or as a zipped batch for a whole project's zones. BUILT FOR THE FIELD • 100% offline — no account, no internet connection required, no ads • No data collection — everything stays on your device • WGS84 and GRS80 ellipsoids • DMS or decimal degree input, your choice of angle format • Designed by a practising survey engineer for real construction-grade accuracy Whether you're laying out a highway through mountain terrain, a metro line, or a cadastral survey, SurveyStar LDP Companion helps you design, verify, and deploy the right local projection — accurately, and without needing a desktop GIS workstation on site.

Initial release. SurveyStar LDP Companion helps surveyors and GIS professionals design, check, and export Low Distortion Projections (LDPs) for construction, cadastral, and infrastructure work — fully offline, no account needed. Includes K0 Calculator, LDP Builder (PROJ/WKT/JobXML export), Distortion Analyst, Projection Advisor (with two free worked examples), and a local LDP library. Feedback welcome!