Units¶
Overview¶
R3Survey uses three independent unit concepts:
- Drawing units — what one model-space unit represents (e.g. 1 drawing unit = 1 metre). This is the internal storage unit and is set on the Length tab of
R3UNITS. - Input units — the unit you type distances in (
R3TRAV,R3OFFSET). R3Survey converts to drawing units automatically. - Display formatting — how values are shown in
R3PROPERTIESand annotation. Changing display settings never modifies stored geometry.
These are configured independently in R3UNITS and can all differ. For example, you can draw in metres, enter distances in feet and inches, and display results in links — R3Survey converts everything automatically.
Length units¶
| Unit | Abbreviation | Metres per unit |
|---|---|---|
| Metres | m | 1.0 |
| Decimal feet (international) | ft | 0.3048 |
| US survey feet | ft (US) | 0.304800609601 |
| Feet and inches | ft in | 0.3048 per foot |
| Links | l | 0.201168 |
| Custom | — | user-defined |
Feet vs US survey feet
The difference between international feet and US survey feet is small (~2 ppm) but matters in high-precision cadastral work. Use US survey feet when working with data from US survey records. Use decimal feet for general imperial work.
Feet and inches input format¶
Feet and inches are entered as: feet.inches-numerator/denominator
| You type | Means |
|---|---|
125.01 |
125' 1" |
125.0112 |
125' 1-1/2" |
0.001516 |
0' 0-15/16" |
66.11 |
66' 11" |
The denominator notation is: inches-numerator/denominator written after the decimal point. Common fractions:
| Fraction | Typed as |
|---|---|
| 1/4" | .00014 → x.0014 |
| 1/2" | x.0012 |
| 3/4" | x.0034 |
| 1/8" | x.0018 |
| 1/16" | x.000116 |
Known issue
Feet and inches input does not currently accept .11 in place of 0.11 (0'-11"). Always include the leading zero for feet.
Area units¶
| Unit | Abbreviation | m² per unit |
|---|---|---|
| Square metres | m² | 1.0 |
| Hectares | ha | 10,000 |
| Square feet | ft² | 0.0929 |
| Acres | ac | 4046.86 |
| Square chains | ch² | 404.686 |
| Perches | p | 25.2929 |
| Custom | — | user-defined |
Custom units¶
You can define custom length and area units in R3UNITS by specifying a conversion factor relative to metres (for length) or square metres (for area). Custom units appear alongside built-in units in all dropdowns.
Switching units during traverse¶
During R3TRAV and R3OFFSET, you can switch input units without exiting the command:
| Type at distance prompt | Effect |
|---|---|
m |
Switch to metres |
f |
Switch to feet and inches |
e |
Switch to decimal feet |
u |
Switch to US survey feet |
l |
Switch to links |
? |
Display keyword help |
The new unit stays active for subsequent legs until changed again.