Two detectorists can work the same farm for a season and come home with very different finds. Usually the difference is not the machine. It is that one of them looked at a map first, and walked to the corner where a building stood in 1842 rather than wandering up and down the middle of a modern field.
Research is the cheapest upgrade in detecting. Everything in this guide is free apart from one book, and most of it you can do at the kitchen table before you ask anyone for permission.
Start with old Ordnance Survey maps
The National Library of Scotland has digitised Ordnance Survey maps covering the whole of Britain — not just Scotland — and put them online for nothing. The useful feature is the side-by-side view: the old map on one side, a modern map or satellite image on the other, locked together as you pan.
Load the six-inch or 25-inch maps from the 1850s to the 1890s and compare them with today. What you are hunting for is anything that was there then and is not there now, because that is ground that has been undisturbed since.
What to look for on an old map
Vanished buildings. A cottage, farm, mill or smithy marked on the 1870s map with nothing there today is the single best target on any map. People lived, worked and lost things on that spot for generations.
Old roads and trackways. Routes that have been replaced or abandoned. Verges of old lanes, and the ground either side of a track that has since been straightened, are where things fell off carts.
Crossroads, fords and bridges. Places where people stopped, waited, paid tolls, watered horses and argued. Fords are especially good — coins have been dropped in them for 2,000 years.
Inns, fairs and markets. An inn marked on an old map, or a field named as a fair ground, means crowds, drinking and money changing hands outdoors.
Churches, chapels and their approaches. Not the churchyard itself, which is off limits, but the paths and fields people crossed to get there.
Parish boundaries. Boundary markers, beating the bounds, and the habit of burying unwelcome things at the parish edge.
Field names. Tithe apportionments list them, and they are full of clues. Chapel Field, Castle Close, Church Piece, Money Field, Gallows Hill, Market Close, Stoney Piece, Blacklands — the last of these often indicates dark occupation soil.
Tithe maps and enclosure awards
Tithe maps were drawn for most English and Welsh parishes between about 1836 and the 1850s, and they are a detectorist’s dream: every field drawn, numbered, and listed in an accompanying apportionment with its name, its owner, its occupier and its use.
They sit earlier than the first detailed Ordnance Survey maps, so they show buildings and boundaries that had already gone by the time the OS arrived. Many county record offices have scanned theirs and put them online free; others have them on microfilm in the search room. Enclosure awards, mostly 1760 to 1840, do a similar job and show the open field system before it was carved up.
LiDAR, satellite images and crop marks
LiDAR is an aerial laser survey that measures ground height to within a few centimetres, and the Environment Agency has released its coverage of England as open data. With the vegetation stripped out digitally, it shows earthworks that are invisible standing in the field: old field boundaries, hollow ways, house platforms, ridge and furrow, quarry pits.
Satellite imagery does something similar for free. Google Earth keeps historical imagery, so you can step back through 20 years of photographs of the same field. In a dry summer, crop marks show buried ditches and walls as darker or lighter lines in the crop. A field that looked ordinary in 2019 might show a complete enclosure in the 2022 drought images.
Check what has already been found nearby
The Portable Antiquities Scheme database holds well over a million recorded finds, each with a findspot and a date. Search your parish and the ones around it. A cluster of Roman coins recorded a field away tells you what period the land holds, and gives you something concrete to mention when you ask the farmer.
While you are there, check the National Heritage List for scheduled monuments. Detecting on one without consent is a criminal offence, and they are not always obvious on the ground.
Turning research into permission
Research also makes the permission conversation easier, because you arrive with a reason rather than a vague request. Saying “the 1871 map shows a building in the corner of your top field and I would love to see what is around it” lands very differently from “can I detect on your land”.
Our guide on getting permission to metal detect covers the approach, and there is a free permission letter template you can adapt — having something in writing reassures farmers more than anything else you can say.
Keep a record of what you find where
Once you are on the land, record as you go. Mark findspots on a phone map or with a GPS app, note the depth and the field, and photograph anything interesting in situ before you lift it. Three reasons: you will spot patterns and work out where the hotspot is, your Finds Liaison Officer needs the location to record a find properly, and a farmer who sees you keeping careful records tends to keep inviting you back.
One book worth owning
Most of this research is free. The exception worth paying for is a book that walks through the whole process of reading maps and documents for detecting sites.
Successful Detecting Sites (about £23)
Walks through exactly this process: reading old maps, using documents and working out which fields are worth asking about. The one book that pays for itself in permissions rather than kit.
Our metal detecting books guide covers the rest, including finds identification books that will save you hours of staring at a corroded lump.
Frequently asked questions
Do I need to pay for old maps? No. The National Library of Scotland’s historic Ordnance Survey maps are free to view online and cover all of Britain. Many tithe maps are free through county archives too.
What is the single best thing to look for on an old map? A building that existed then and does not now, especially an isolated one.
Is LiDAR data free in the UK? The Environment Agency’s coverage of England is free open data. Wales and Scotland have their own releases with different coverage.
Does research work on beaches? Less so, because the sand moves. There, old photographs of piers, bathing areas and vanished lidos are more useful than maps.
Can I detect anywhere I find on a map? No. Every piece of land in Britain belongs to somebody, and you need the landowner’s permission. Research tells you which permission is worth asking for.