Basic terrain will probably look like this (more details on different terrain types in TFTD
https://www.ufopaedia.org/index.php?title=TERRAIN_%28TFTD%29)
terrains:
- name: PIPES
mapDataSets:
- BLANKS
- SEA
- ISLAND1
- ISLAND2
- ISLAND3
largeBlockLimit: 5
mapBlocks:
- name: ISLAND00
width: 10
length: 10
type: 1
subType: 0
maxCount: 3
- name: ISLAND01
width: 10
length: 10
maxCount: 3
- name: ISLAND02
width: 20
length: 20
maxCount: 3
- name: ISLAND03
width: 20
length: 20
maxCount: 3
- name: ISLAND04
width: 20
length: 20
maxCount: 3
- name: ISLAND05
width: 20
length: 20
maxCount: 3
- name: ISLAND06
width: 20
length: 20
maxCount: 3
- name: ISLAND07
width: 10
length: 10
maxCount: 3
- name: ISLAND08
width: 10
length: 10
maxCount: 3
- name: ISLAND09
width: 10
length: 10
maxCount: 3
- name: ISLAND10
width: 10
length: 10
maxCount: 3
- name: ISLAND11
width: 10
length: 10
maxCount: 3
- name: ISLAND12
width: 10
length: 10
maxCount: 3
- name: ISLAND13
width: 10
length: 10
maxCount: 3
- name: ISLAND14
width: 10
length: 10
maxCount: 3
With ISLAND terrain you need the following files
TERRAIN/SEA.MCD, .PCK and .TAB
TERRAIN/ISLAND01.MCD, .PCK and .TAB (possibly .LBM?)
TERRAIN/ISLAND02.MCD, .PCK and .TAB (possibly .LBM?)
TERRAIN/ISLAND03.MCD, .PCK and .TAB (possibly .LBM?)
MAPS/ISLAND00.MAP - ISLAND14.MAP