I spent the last two days tromping through the back country of northern Taiwan in search of more of the wall.  A lot of it has been destroyed by factories and housing estates.  The depressing thing is that most of the destruction has happened in the last 20 years.  Something that has survived for over 200 years is being destroyed in our life time. 

I've been searching for the wall by first searching on maps for placenames that refer to the wall like "earthen ox" or "ox hill" or "earthen village" or "division spot (referring to the division of Han vs aboriginals the wall create)."  But these names are few (total of only 25 so far found) and far between (literally).  There is so much ground to cover in between these few place names so the only way is to get out there and search.

The next source of information is reading history records.  But not many records were kept of the wild frontier of 250 years ago.  And what records exist are spotty and/or vague (they refer to an area the wall went through, no specific location).  Another problem is the place names for most of the route have changed so even if I could identify a place, the locals don't necessarily know which modern name has replaced the old name

I have yet to find a detailed map that shows locations for the wall.  The closest resolution I can get is MILES, not yards or feet! 

One good thing is that because the wall was constructed by the government, the land on which it stood was public property.  When the Japanese took control of Taiwan in the late 1800's they maintained the public property registry for the land the wall was on.  This category has been maintained until now.  This means that the land the wall is on should technically off limits to private individuals.  In many places this exclusion has been maintained.  What has happened is that in places the public land has been used for public purposes.  The wall has been pulled down and replaced with a road.  The ditch has been widened into a canal.  In other places the land has been abandoned and has become overgrown.  But due to the unique nature of the wall (meters wide, miles long), the abandoned land is in long strips that can be seen from a satellite as a line that is different in color and usage than the surrounding plots of land.  Parts that have been converted into canals or roads can be linked together with the abandoned strips of land to form long sections if one knows what to look for on a satellite map.

Thus the best way to find where the wall used to go is to use satellite imagining to locate lines that are suspiciously straight or follow the contours of the land in man-made ways.  Then I take the map and the coordinates and drive out to the location and ask local farmers what the site I located on the map is.  About 10% of the time I find someone that can lead me to a portion of the wall.  Mostly the locals just stare at me as though I'm crazy.