Project File
No project JSON loaded.
Saves project settings, State Plane selection, datum/ellipsoid, GRID points, Ground/LDP settings, and QA preferences. GEOID binary data is not embedded; the project stores the GEOID filenames and the remembered-file feature can reconnect them.
1. Load GRID Coordinates
Drop GRID coordinate file here
TXT, CSV, ASC, PNEZD or similar coordinate file
Or tap/click this box to browse.
Accepts GRID-coordinate TXT, CSV, ASC, PNEZD and other plain-text files. Comma, tab, semicolon and whitespace delimiters are supported. Point IDs may be numeric or alphanumeric (for example 1A, 1B, 61X). Header rows are skipped automatically.
INPUT REQUIREMENT — GRID COORDINATES ONLY
Imported Northing/Easting coordinates must be GRID coordinates in the selected State Plane coordinate system. Do not load previously scaled ground, local, modified, or already grid-to-ground-converted coordinates. Doing so would apply the correction a second time and produce incorrect coordinates.
Imported Northing/Easting coordinates must be GRID coordinates in the selected State Plane coordinate system. Do not load previously scaled ground, local, modified, or already grid-to-ground-converted coordinates. Doing so would apply the correction a second time and produce incorrect coordinates.
No points loaded.
Input QA will run when a GRID file is loaded.
2. Datum / Projection
Datum selection tells the app what datum the input State Plane coordinates are already on; it does not transform coordinates from one datum to another. The built-in zone definitions cover the standard SPCS83 zones for all 50 states. NAD83 realizations use GRS 1980; Hawaii's official modern zone definitions use NAD83(PA11). Selecting a different datum does not transform coordinates—it applies that datum/ellipsoid to the selected SPCS83 projection geometry.
Geographic zone QA will run after GRID points are loaded.
3. Vertical / GEOID18
Preferred on Edge/Chrome: use Choose & Remember GEOID File. The browser stores a secure file handle (not the visible Windows path) and can reopen the same GEOID file later if permission remains available. The normal file picker remains available as a fallback. Designed for NGS GEOID18
g2018*.bin tiles.No remembered GEOID file.
No geoid grid loaded.
Project GEOID coverage will be checked before calculation.
Enter N in the selected elevation units. The app uses h = H + N.
The app interpolates geoid separation at each point after converting the State Plane coordinate to latitude/longitude. Geoid grid values are interpreted in meters.
4. Output Coordinate System
LDP workflow: Input remains the selected State Plane GRID. Output is a custom LDP GRID designed to keep the combined factor near 1.000000 across the project. LDP coordinates are grid coordinates—not scaled ground coordinates.
The design helper centers a Transverse Mercator projection on the project and solves k₀ so the average LDP combined factor is approximately 1.000000 at the loaded project elevations. Review the parameters and distortion before adopting the LDP.
Load and confirm State Plane GRID points to design an LDP.
Origin: Project Centroid — load points to calculate.
5. Calculate / Export
Project number, date, and creator name are included in the four-coordinate-table CSV and PDF. The PDF repeats the project/date, datum, coordinate system, CACF, table title, and column headers on every page.
Load GRID coordinates and confirm the input type before calculating.
Four-table export will be available after calculation.