The short answer
Choose the EPSG code of the projected coordinate system your survey data was delivered in, and set the drawing units before you import. For grid resolution, use a spacing close to your pile spacing on sites with survey data, go coarser on very large sites, and never go finer than the data itself. Most terrain that lands in the wrong place or shows the wrong area comes from a units mismatch or a wrong EPSG code, not from the terrain data.
1. Where each importer takes the coordinate system from
The four importers on the Terrain Import panel handle the coordinate system differently:
- Import KML/KMZ: no choice needed. KML is always latitude and longitude, and PVX.AI projects it into the UTM zone of the boundary. The elevation data is downloaded for that boundary.
- Import LAS/LAZ: reads the coordinate system from the file header and shows Detected from LAS header. If the header has none, it shows Coordinate system not detected and you must pick one before you continue.
- Import TXT/CSV: the coordinate system is optional. With one, PVX.AI reprojects the points. Without one, the coordinates are used as they are, so they must already be in the drawing’s coordinate system, and location-based features (sun position) are not set.
- Import Contours: the coordinate system is optional and never moves the contours. They stay at their drawing coordinates. The code is used only to locate the site on the globe, for sun position, KML export and soil analysis. Click No Coordinate System Information if you do not have one.
Where a picker appears, type the EPSG code or part of the name in Search EPSG code or name… to find it.
2. Which EPSG code do I enter?
Enter the code of the system the surveyor used, not one that looks close. Look for it in the survey report, in the .prj file delivered with the data, or in the drone processing report. It is usually a national grid, a UTM zone, or a State Plane zone.
- US State Plane in US survey feet: pick the US survey feet variant of the zone (often marked ftUS). PVX.AI converts these codes at the exact survey foot, and drawings set to US survey feet are read the same way.
- Latitude and longitude in degrees: convert the points to a projected coordinate system first, usually the UTM zone of the site, and import that file with the matching EPSG code. TXT/CSV import expects coordinates in metres or feet. KML and KMZ files are the exception: they are always in latitude and longitude, and the KML import handles them directly.
- KML export: if the code you chose cannot be converted for Google Earth, Design (KML) export refuses it and asks you to choose another system, instead of writing a file in the wrong place.
What to do: follow the importer guide for your data: Importing Contour Lines, Importing Point Cloud (Drone) Data, Importing Z-Points or Importing KML Files.
3. My terrain lands in the wrong place or shows the wrong area
Check these in order:
- Drawing units. PVX.AI reads the units from the drawing (the AutoCAD INSUNITS setting). A unitless drawing and a millimetre drawing are both treated as metres, and an inch drawing as feet. If your data is in feet but the drawing says metres, every distance and area is off by a factor of about 3.3. Set the drawing units to match the data before importing. See AutoCAD Versions, Language, and Units.
- Wrong EPSG on a point cloud or point file. For LAS/LAZ and TXT/CSV, the code decides where the points are moved to. A wrong code puts the terrain in the wrong place or distorts it.
- Contours or points mixed with other data. In Import Contours, use the Search layers… box to tick only the layers that hold contours or spot heights. Text far from the other elevation points makes PVX.AI ask whether to leave those layers out.
- A point file with no coordinate system, whose coordinates are not in the drawing’s system. Either pick the right code, or convert the file first.
4. Which grid resolution should I use?
Grid resolution is the distance between neighbouring points of the terrain grid. A lower value gives more detail and a heavier drawing; a higher value is faster. Every later step (grading, adapting terrain to piles, collision checks, volumes) works on this grid, and once terrain exists in the drawing the resolution is locked for the rest of the project. Choose it on the first import.
- Defaults and limits: Import KML/KMZ 10 m (3 to 25 m), Import LAS/LAZ and Import TXT/CSV 3 m (1 to 25 m), Import Contours 10 m, or 33 ft in feet drawings (0.5 to 25 m). In feet drawings the box shows feet.
- Sites with survey data: use a spacing close to your pile spacing along the row, so pile reveals and cut/fill are measured at the level of detail the piles need.
- Large sites: 10 to 15 m keeps the drawing workable. For very large sites, around 500 MW and up, split the site into several PV areas or drawings.
- Do not go finer than the data. A grid finer than the point spacing of the survey, or than the 30 m source used for KML elevation downloads, adds no detail, only weight.
- Size limit: one import can create up to 8 million grid cells. That is roughly an 8.5 km square at 3 m, or 28 km at 10 m. Above that, PVX.AI refuses the import before charging any credits and asks you to increase the spacing or import a smaller area.
A 5 m grid on a large site is slow because the number of grid points grows with the square of the site size: halving the spacing gives four times as many points. If grading or analysis is slow, a coarser grid on the first import is the main lever.
5. Check the terrain before you design on it
After importing, check the site is where you expect it (compare it with a satellite image or the boundary KML) and that the area matches the survey. On the Terrain Settings tab of any import window, turn on Show Directional Slope Map (EW/NS) and adjust the Slope Analysis Ranges to see slopes in the directions that matter for your racks. Use Create Specific Legend on the Terrain panel to get a slope legend for one area only.
More on what PVX.AI does with terrain is on the terrain analysis page on pvx.ai.