CS, SA, RS, BS: Which New Dag Is Your Old Dag? Comparing Survey Maps

Every new survey redraws the mouza map and numbers the dags afresh. One dag splits into several, several merge into one, a road or canal moves a boundary. So searching a new map with an old khatian’s dag number often lands on someone else’s land. The only reliable way is to lay the two survey maps side by side and match the place itself.

The surveys, oldest to newest

Dates vary by district, but roughly in this order:

• CS (Cadastral Survey): British period, roughly 1888 to 1940. The first plot-by-plot survey; still the root of title for old ownership.
• SA (State Acquisition): after the zamindari system was abolished, the late 1950s to the early 1960s. In many places its maps stay very close to the CS maps.
• RS (Revisional Survey): the 1960s to the 1990s, by district. It revised the earlier surveys with new possession and divisions; across much of the country it has long been the working record.
• BS / BRS / City Survey: the national survey after independence, still under way or recently published in many districts; in cities it is called the City Survey. Today’s dag numbers are here.
• Diyara survey: a special survey of newly risen char land and riverbanks, where erosion and accretion keep moving the boundaries.

The idea behind matching two maps

The two maps were drawn at different times by different hands; even at the same scale, shrunk paper and drawing differences mean they never line up exactly. So you pick a few places present on both — an old road junction, a canal crossing, a bridge, a mouza boundary corner — and match those. Once those points agree, the rest of the map roughly agrees too, and you can see which old dags lie under each new dag, and by how much.

Step by step

1. Get two survey maps of the same mouza

For example the RS and BS maps of one mouza. Set the scale of both (usually 16 inches = 1 mile). Check the sheet numbers: the same area can fall on different sheets in different surveys.

2. Draw the dags on both maps

On each map, outline the dags you want to compare, corner by corner, and name them by dag number: your dag on the new map, and the dags around it on the old one.

3. Set the same points on both maps

Choose places that exist in both surveys, close to the dags. Two points are the minimum; three or four on different sides fit better. Skip riverbanks and pond edges — they move from survey to survey.

4. Read which dag lies under which

Once matched, the old dags sit over each new dag. A real example from a mouza in Chattogram:

• BS dag 4971 (18.946 decimal): under it lie 14.818 decimal of RS dag 1815 — 78% of the BS dag and 67% of the RS dag — and 18.847 decimal of CS dag 1815 — 99% of the BS dag and 55% of the CS dag.
• BS dag 5029 (4.908 decimal): mostly (82%) RS dag 1820, a little (14%) RS dag 1819; 92% CS dag 1820.

Read the two percentages together: “% of this dag” says where the new dag came from; “% of that dag” says how much of the old dag fell here — the rest went into other new dags.

Mistakes to avoid

• Matching dag numbers alone. The same number in an old and a new survey is not the same land — almost never.
• Matching on distant points. Two points in one corner of the sheet leave dags at the other end off. Use points close around the dags.
• Picking places that change. Rivers, canals, ponds and new roads move between surveys.
• Treating the result as final. Old maps are hand-drawn; the fit is good near the points and weaker far away. Thin sliver overlaps are usually matching error, not land. For legal matters, an amin and the land office decide.

In short

To find an old dag, match the place, not the number: draw the dags on two survey maps of the same mouza, set a few points present in both, and read which old dags lie under each new dag and by how much. The last two surveys are usually enough; go back to CS when you need the root of title.

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