Accuracy
How accurate are the maps?
Every battle in the atlas carries an accuracy score out of 100: how sure we are of where the units stood and moved. It is not a grade of the history itself, only of the positions on the map. Here is how it is worked out.
The four parts of the score
- Sources (up to 40). What the positions are traced from. 40: an official survey or atlas made from field study, such as the 1904 Antietam Battlefield Board atlas, Craan's 1816 survey of Waterloo or the US Army's 1945 Omaha Beachhead maps. About 30: a detailed period or park-derived map. About 25: a modern reconstruction built on park sites. About 15: a reconstruction from written accounts with no troop map.
- Fixed points (up to 30). How well the map is pinned to the real ground by things that can be checked independently: battlefield markers and monuments, archaeology, surviving buildings, roads and streams. 30: they agree within about 50 metres; 22: about 150 m; 15: about 300 m; 8: worse.
- Movement detail (up to 20). How finely the units move from stage to stage. 20: regiments or brigades, stage by stage; 14: divisions; 8: schematic arrows and blocks.
- Corroboration (up to 10). Whether independent sources (markers, archaeology, official histories, eyewitnesses on both sides) agree with each other.
What the bands mean
- 85–100, high. Units placed from a survey-grade source and checked against the ground; expect positions within tens of metres.
- 70–84, good. A solid map source with good fixed points; most positions within about 100 metres.
- 60–69, moderate. The overall shape is right, but some positions are estimated from distances or descriptions.
- Below 60, limited. A careful reconstruction from accounts and a few fixed points. Trust the story and the terrain more than exact spots.
Approximate places, marked ≈
Inside each battle, landmarks and units that are only approximately located are marked ≈. Tap one on the map, or open the "Approximate locations" list in the Overview tab, to see why: no surviving marker, placed by distance from a period account, sources that disagree, and so on. Each battle's Overview also lists where its positions come from.
Every battle's score
| Battle | Total | Sources /40 | Fixed points /30 | Movement /20 | Corroboration /10 | Band |
|---|---|---|---|---|---|---|
| Waterloo 1815 | 92 | 40 | 28 | 16 | 8 | high |
| Antietam 1862 | 92 | 40 | 24 | 20 | 8 | high |
| Omaha Beach 1944 | 86 | 40 | 22 | 16 | 8 | high |
| Yorktown 1781 | 84 | 32 | 24 | 18 | 10 | good |
| Gettysburg 1863 | 82 | 32 | 22 | 20 | 8 | good |
| Little Bighorn 1876 | 79 | 25 | 28 | 16 | 10 | good |
| Ia Drang 1965 | 77 | 25 | 22 | 20 | 10 | good |
| The Alamo 1836 | 75 | 25 | 30 | 14 | 6 | good |
| Hue 1968 | 75 | 25 | 22 | 20 | 8 | good |
| San Jacinto 1836 | 73 | 25 | 22 | 20 | 6 | good |
| First Bull Run 1861 | 73 | 25 | 22 | 20 | 6 | good |
| Belleau Wood 1918 | 73 | 25 | 22 | 20 | 6 | good |
| Bunker Hill 1775 | 72 | 28 | 22 | 14 | 8 | good |
| Saint-Mihiel 1918 | 72 | 30 | 22 | 14 | 6 | good |
| Saratoga 1777 | 71 | 30 | 19 | 16 | 6 | good |
| Trenton 1776 | 70 | 22 | 22 | 18 | 8 | good |
| Kings Mountain 1780 | 70 | 22 | 22 | 18 | 8 | good |
| Quatre Bras and Ligny 1815 | 67 | 25 | 22 | 14 | 6 | moderate |
| Midway 1942 | 67 | 30 | 15 | 16 | 6 | moderate |
| Iwo Jima 1945 | 67 | 25 | 22 | 14 | 6 | moderate |
| New Orleans 1815 | 66 | 22 | 22 | 16 | 6 | moderate |
| Cowpens 1781 | 65 | 22 | 18 | 18 | 7 | moderate |
| Shiloh 1862 | 65 | 28 | 18 | 13 | 6 | moderate |
| Chickamauga 1863 | 65 | 28 | 15 | 16 | 6 | moderate |
| Hattin 1187 | 64 | 28 | 17 | 12 | 7 | moderate |
| Chapultepec 1847 | 64 | 25 | 15 | 18 | 6 | moderate |
| Chancellorsville 1863 | 60 | 25 | 15 | 14 | 6 | moderate |
| Fort Wagner 1863 | 60 | 25 | 15 | 14 | 6 | moderate |
| St Eloi Craters 1916 | 58 | 20 | 18 | 14 | 6 | limited |
| Chosin Reservoir 1950 | 58 | 25 | 10 | 15 | 8 | limited |
| Siege of Acre 1189 | 57 | 22 | 18 | 10 | 7 | limited |
| Arsuf 1191 | 57 | 26 | 16 | 9 | 6 | limited |
| San Juan Hill 1898 | 57 | 22 | 15 | 14 | 6 | limited |
| Jacob's Ford 1179 | 56 | 26 | 19 | 6 | 5 | limited |
| Wagon Box Fight 1867 | 55 | 15 | 21 | 10 | 9 | limited |
| Siege of Jerusalem 1099 | 54 | 22 | 22 | 6 | 4 | limited |
| Guadalcanal: Mount Austen 1942 | 52 | 24 | 12 | 12 | 4 | limited |
| Fetterman Fight 1866 | 51 | 15 | 18 | 10 | 8 | limited |
| Second Battle of Adobe Walls 1874 | 44 | 15 | 15 | 8 | 6 | limited |
| Pecos River Fight 1875 | 42 | 18 | 8 | 10 | 6 | limited |
| Montgisard 1177 | 37 | 15 | 7 | 8 | 7 | limited |
Spotted something in the wrong place? Use "Report a problem" in the atlas. Corrections backed by a source are always welcome.