Map Grid Cell Origin Sign Tool

Description

Offset the origin by column plus one half horizontally and signed row plus one half vertically.

A geographic grid uses indexes, tile sizes, origins, and cell spacing. Row direction and floor-division policy determine where cells fall, especially for negative indexes or origins defined at an outer corner.

Offset the origin by column plus one half horizontally and signed row plus one half vertically.

When to use this tool

Use Map Grid Cell Origin Sign when you need an explicit grid-index or angular-resolution calculation.

How to use the tool and how it works

Enter column, row, xOrigin, yOrigin, cellWidth, cellHeight, rowDirection. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read centerX, centerY. Use the output convention below.

Require nonnegative integer row and column, positive cell dimensions, and rowDirection up or down. Offset the origin by column plus one half horizontally and signed row plus one half vertically.^[1]

Input field	Meaning and units	Accepted input
column	Column	Required. Safe integer; minimum 0.
row	Row	Required. Safe integer; minimum 0.
xOrigin	X Origin	Required. Finite number.
yOrigin	Outer-corner y coordinate in a positive-up coordinate frame.	Required. Finite number.
cellWidth	Cell Width	Required. Finite number; strictly above 0.
cellHeight	Cell Height	Required. Finite number; strictly above 0.
rowDirection	Down decreases y; up increases y.	Required. Text; one of "up", "down"; maximum UTF-16 length 8192.

Output field	Interpretation	Returned shape
centerX	Center X	Required. Finite number.
centerY	Center Y	Required. Finite number.

json

{
  "input": {
    "column": 0,
    "row": 1,
    "xOrigin": 100,
    "yOrigin": 200,
    "cellWidth": 10,
    "cellHeight": 20,
    "rowDirection": "down"
  },
  "output": {
    "centerX": 105,
    "centerY": 170
  }
}

Limitations and assumptions

The coordinate y axis is positive upward, so down rows decrease y. The supplied origin is an outer cell corner, not the first center; no map projection or raster extent is inferred.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Use the raster's actual georeferencing transform for geographic placement. Verify corner versus center origin, axis direction, tile dimensions, and bounds before combining index calculations.

References

Calculation and input contract: geography/map-grid-cell-origin-sign — tool.io

Similar or alternative tools

Geographic Grid Cell Local Index
Return floor-divided tile indexes and nonnegative modular local indexes for the supplied column and row.
Geography: Geographic Cell Angular Center
Compute the eastward wrapped longitude span, take its halfway point, and normalize into [-180, 180).