Field guide
Read the line between two survey points
An inverse is straightforward once the origin, axes and reference are explicit. Use this guide to keep those choices visible in the result.
Start with a directed pair, not just two numbers
A survey inverse answers a practical question: how far away is point B, and in which direction does it lie when viewed from point A? The order matters. The same two locations have one horizontal separation, but reversing the origin changes the direction by half a turn. Use the point identifiers and source lines to establish that order before reading an angle. A wrong origin can produce a mathematically valid result that describes the opposite operation.
This bearing and distance calculator works with easting and northing in a shared planar coordinate frame. It is useful for checking a drawing baseline, reviewing a proposed connection, or explaining a coordinate difference to a colleague. It does not establish the coordinate reference of an unfamiliar file. Keep the project notes, control information and file revision alongside the calculation.
Read the axes before choosing the records
Easting is the coordinate increasing toward the east of the working grid; northing increases toward its north. A column called X is not sufficient evidence of either meaning. Different surveying and CAD conventions use those letters differently. Confirm the source specification, then map the fields explicitly. Swapping both axes can preserve the distance while changing the direction, making an apparently reasonable distance a poor check of the mapping.
The file importer accepts UTF-8 CSV or TXT with comma, semicolon or tab delimiters. Review the first rows, choose whether a header is present, and confirm the horizontal and elevation units. The unit selectors label the values already supplied. They do not convert feet to metres or make different coordinate systems compatible. XLSX workbooks are also accepted for this input: explicitly choose the worksheet, and replace formulas, dates or error cells with plain values before importing.
Choose one pair or a reproducible batch
For a single calculation, enter the two eastings and northings in the A and B cards. Point names and heights are optional. The example button supplies clearly marked synthetic coordinates, so you can check the interface before using project data. The swap button exchanges every field between the two cards, including height, without overwriting an uploaded file.
For a batch, read a point file and add pairs using the actual physical start line of each record. Line numbers include the header and any preceding blank lines; a quoted multiline record uses its first physical line. The list starts with from_line,to_line. This deliberate mapping also works when two records share the same point name. There is no silent matching by approximate coordinates or duplicate identifiers.
What the coordinate differences mean
The horizontal increments are destination minus origin: delta E equals E(B) minus E(A), and delta N equals N(B) minus N(A). Positive delta E points east; positive delta N points north. The horizontal distance is the square root of delta E squared plus delta N squared. An increment can be negative, while a distance is never negative.
With A at E 100, N 200 and B at E 200, N 300, both increments are 100. The horizontal distance is approximately 141.421356 in the chosen horizontal unit. Its azimuth is 45 degrees. These are synthetic numbers for checking the convention, not a field measurement or an acceptance tolerance.
Azimuth, quadrant bearing and the reverse direction
Azimuth is measured clockwise from coordinate north: north is 0 degrees, east 90, south 180 and west 270. The calculation uses both signed increments to identify the correct quadrant. Taking an ordinary arctangent of one divided by the other without quadrant handling would fail for several directions and for some axis-aligned lines.
A quadrant bearing expresses the same direction using north or south, an angle from zero to ninety degrees, and east or west. For example, an azimuth of 135 degrees is S 45° E. Cardinal directions are shown simply as N, E, S or W. The reverse azimuth is the forward azimuth plus 180 degrees, wrapped into a full turn. It describes B to A, not a separate observation.
Keep horizontal distance separate from height
When both records contain a valid elevation, the tool also subtracts their heights. The sign of delta Z tells you whether the destination is higher or lower in the supplied height reference. A missing value remains unknown. Entering zero is an explicit height value, so do not use it merely to fill an empty cell.
A three-dimensional straight-line coordinate distance is available only when both heights exist and the horizontal and vertical units match. It combines the horizontal separation and height difference using the same right-triangle relationship. It is not an instrument slope-distance reduction: no atmospheric, prism, curvature or refraction corrections are applied. Different unit labels still allow the horizontal result and the separately labelled height difference, but prevent the combined distance.
Coincident points need an honest result
If both planar coordinates are equal, the horizontal distance is zero and the planar direction is undefined. There is no unique north, east or any other direction from a point to itself. The tool reports a coincident pair and leaves azimuth and quadrant bearing empty instead of inventing a zero-degree bearing.
Two points can share their planar position while having different heights. Their height difference and three-dimensional distance can still be meaningful, subject to valid inputs and matching units. Inspect the raw values in the selected-pair detail before deciding whether a coincident pair is an intentional vertical comparison, repeated observation or source-data mistake.
Coordinate north is not automatically true north
The angle is relative to the north axis of the supplied coordinate frame. It is not automatically a true bearing or a magnetic bearing. A drawing rotation, grid convergence or magnetic declination requires context outside the two point records. The calculator does not infer those corrections from coordinate magnitudes or a place name.
Likewise, a coordinate distance is not automatically a ground distance. Projection and elevation scale factors can produce a difference between a grid inverse and a distance measured on site. Record the applicable reference in the workspace. If the project needs a ground-to-grid workflow, use its documented transformations before comparing these values with observations.
Why latitude and longitude belong elsewhere
Longitude and latitude are angles on a geographic reference system. Feeding decimal degrees into a planar distance formula does not return metres, even if the result resembles a small local distance. This tool requires confirmation that the data is planar and deliberately provides no latitude/longitude mode.
Coordinate magnitudes alone cannot reliably distinguish local planar values from geographic degrees. A small engineering grid may legitimately contain values such as 100 and 200. Verify the coordinate system from the source owner or project documentation; convert using an appropriate projected or geodetic workflow when required. Renaming a column or selecting metres does not perform that conversion.
Review every listed pair, including failures
The result table preserves the order of your pair list. A selected source record with a validation error produces an unresolved result, rather than being removed from the batch. A source line that does not identify a record stops the calculation with the line number to correct. This avoids shifting the meaning of later rows.
Select a numbered result to see both original coordinate texts, source names and line numbers. The plot uses coordinates relative to the selected origin, with north up and east right. It is a direction aid, not a map. A short line at a large coordinate origin can therefore remain visible without pretending to add measurement precision.
Precision, limits and a useful handover
Coordinate strings are subtracted as decimals before the difference is converted for trigonometry. This preserves small differences that could otherwise disappear when two large origins are independently rounded to binary floating point. Distances and angles still use numerical floating-point calculations. Values outside the supported numeric range are reported as unavailable rather than producing an infinite or misleading answer.
The table displays six decimal places for ordinary distances and eight decimal degrees for angles. Very small or large values use scientific notation. Display precision does not certify survey accuracy. CSV azimuths retain numerical calculation precision, while the readable quadrant bearing is rounded to eight decimal degrees. Keep the source and JSON record for a repeatable check.
Point files are limited to 10 MiB and 100,000 records. Pair lists are limited to 2 MiB and 100,000 calculations, with a 10 MiB results CSV limit. The table pages through all results; its page size does not restrict export. Changing an input discards the previous result so that an old download cannot be confused with new settings. Cancellation retains inputs, and clearing the session leaves already downloaded files on your device.