geojson precision

[Robinlovelace]

Thanks for an awesome package.

I've used it for work and all went well until I looked at the object that I created.

I definitely saved a polygon representing the roof space of this site plan but plot(r_new2$finished$geometry) came out like this (it should be a nice curve following the roof which was what I drew):

Any ideas why? Have others reported this - can retry if I discover what I'm doing wrong (I did some re-editing).

Here's some partitially reproducible code, which geo-referenced the raster - that was very useful!

geocompx/geocompr#77

[timelyportfolio]

That is very unfortunate. I will look into this problem. For reference, does it seem to be a precision issue? loss of points/nodes problem?

[Robinlovelace]

Trying to reproduce and save the result in a gif. Example of not reproducing it:

[Robinlovelace]

Update: I think I can reproduce the issue and suspect it's due to zooming. .gif example to follow...

[Robinlovelace]

Maybe panning and zooming in combination:

[Robinlovelace]

[Robinlovelace]

Update: I could reproduce the issue only panning at a single zoom level so now suspect it's more about panning.

[Robinlovelace]

Update: I think this issue only occurs at high zoom levels: that's why I cannot reproduce in the first .gif example. Just tried the same thing at a high zoom level and the result looks garbled.

[tim-salabim]

Yes I can confirm. Whatever is Polygons drawn beyond a zoom level of about 15 seem garbled. Lines and points seems to be equally displaced. @timelyportfolio does this confirm your suspicion of a coordinate precision problem?

[timelyportfolio]

Strange. Here was my first test. I found a random lake in Canada and traced at zoom level 14 in Chrome. I then used editFeatures to try to trace at zoom level 16. Here is the result (note I got lazy and did not complete the trace).

Test 1 in Chrome

library(sf)
library(mapview)
library(mapedit)

# at zoom level 14 create a polygon with mapedit
#   to use for testing
p1 <- structure(list(structure(list(structure(c(-76.1935, -76.1922, 
  -76.191, -76.1904, -76.1902, -76.19, -76.1891, -76.1876, -76.1864, 
  -76.1862, -76.1862, -76.1862, -76.1857, -76.1848, -76.1834, -76.1819, 
  -76.1806, -76.1783, -76.1774, -76.1764, -76.1756, -76.1745, -76.1728, 
  -76.1722, -76.1712, -76.1699, -76.1692, -76.168, -76.1662, -76.1657, 
  -76.1647, -76.1638, -76.1627, -76.1616, -76.1608, -76.1596, -76.1595, 
  -76.1595, -76.1586, -76.1573, -76.1574, -76.1568, -76.1569, -76.1569, 
  -76.156, -76.1563, -76.1566, -76.1572, -76.1583, -76.1589, -76.16, 
  -76.161, -76.162, -76.1631, -76.1639, -76.1651, -76.167, -76.1677, 
  -76.1686, -76.1691, -76.1696, -76.1696, -76.1698, -76.1705, -76.1709, 
  -76.1712, -76.1711, -76.1715, -76.1743, -76.1777, -76.1803, -76.1813, 
  -76.182, -76.1828, -76.1844, -76.186, -76.1875, -76.1891, -76.1904, 
  -76.1918, -76.1936, -76.1949, -76.1959, -76.1968, -76.1971, -76.1976, 
  -76.1975, -76.197, -76.1962, -76.1956, -76.1951, -76.1943, -76.1935, 
  45.1188, 45.1186, 45.1187, 45.1192, 45.12, 45.1205, 45.1213, 
  45.122, 45.1224, 45.1232, 45.1239, 45.1244, 45.1249, 45.1255, 
  45.1259, 45.126, 45.1257, 45.1256, 45.126, 45.1262, 45.1262, 
  45.1259, 45.1259, 45.1257, 45.1254, 45.1249, 45.1245, 45.1248, 
  45.1244, 45.1239, 45.1236, 45.1234, 45.1238, 45.1236, 45.1232, 
  45.1233, 45.1242, 45.1248, 45.1248, 45.1248, 45.1237, 45.1229, 
  45.1224, 45.121, 45.1198, 45.1187, 45.1179, 45.1174, 45.1178, 
  45.1166, 45.1156, 45.1146, 45.1141, 45.1135, 45.1133, 45.1127, 
  45.1124, 45.1128, 45.1131, 45.1138, 45.1144, 45.1156, 45.1161, 
  45.1164, 45.1151, 45.1135, 45.1124, 45.1119, 45.1116, 45.1118, 
  45.1114, 45.1121, 45.1126, 45.1128, 45.1131, 45.1131, 45.1136, 
  45.1138, 45.1141, 45.1141, 45.1141, 45.1141, 45.1144, 45.1146, 
  45.1151, 45.1157, 45.1165, 45.1171, 45.1176, 45.1181, 45.1182, 
  45.1186, 45.1188), .Dim = c(93L, 2L))), class = c("XY", "POLYGON", 
  "sfg"))), n_empty = 0L, precision = 0, class = c("sfc_POLYGON", 
  "sfc"), bbox = structure(c(-76.1976, 45.1114, -76.156, 45.1262
  ), .Names = c("xmin", "ymin", "xmax", "ymax"), class = "bbox"), crs = structure(list(
  epsg = 4326L, proj4string = "+proj=longlat +datum=WGS84 +no_defs"), .Names = c("epsg", 
  "proj4string"), class = "crs"))


editFeatures(st_sf(p1))

Test 2 in RStudio Viewer

I suspected the issue might be RStudio Viewer, but this test seems to yield expected results.

Test 3 Zoom from 16 to 18 during draw

Then, I thought maybe the error is caused by zooming to different levels during the draw, but everything seemed fine.

Test 4 Edit Original at zoom 18

I think I finally experienced the problem when I did editFeatures(p1) and zoomed to level 18 to edit the contour. My edit was much closer to the creek or offshoot than what appears below, so I will classify this as a replication.

[tim-salabim]

Here's an addition I drew to @timelyportfolio 's example using tst = editMap(mapview(p1)). I did the drawing in RStudio viewer at zoom level 17. I tried to follow @timelyportfolio 's outline as close as possible (i.e. replicate his vertices) for a small portion outside the lake. It turns out that I apparently did a very good job as all vertices seem to be topologically identical :-)

tst = structure(list(X_leaflet_id = 87L, feature_type = "polygon", 
    geometry = structure(list(structure(list(structure(c(-76.1705, 
    -76.1698, -76.1696, -76.1696, -76.171, -76.1709, -76.1705, 
    45.1164, 45.1161, 45.1156, 45.1144, 45.1144, 45.1151, 45.1164
    ), .Dim = c(7L, 2L))), class = c("XY", "POLYGON", "sfg"))), n_empty = 0L, precision = 0, class = c("sfc_POLYGON", 
    "sfc"), bbox = structure(c(-76.171, 45.1144, -76.1696, 45.1164
    ), .Names = c("xmin", "ymin", "xmax", "ymax"), class = "bbox"), crs = structure(list(
        epsg = 4326L, proj4string = "+proj=longlat +datum=WGS84 +no_defs"), .Names = c("epsg", 
    "proj4string"), class = "crs"))), .Names = c("X_leaflet_id", 
"feature_type", "geometry"), row.names = 1L, sf_column = "geometry", agr = structure(c(NA_integer_, 
NA_integer_), class = "factor", .Label = c("constant", "aggregate", 
"identity"), .Names = c("X_leaflet_id", "feature_type")), class = c("sf", 
"data.frame"))

mapview(p1) + tst

[Robinlovelace]

Here are some more experiments.

Reproducible example (sorry about all the pkgs!) to geocode a building just south of Willow Terrace at Zoom Level 18:

Slightly garbled output:

[Robinlovelace]

And taking more care (zoom level: 19 in Firefox):

[Robinlovelace]

The result makes me think it's a precision/snapping issue:

[Robinlovelace]

Please try to reproduce this simple example with the code below:

library(sf)
library(mapview)
library(mapedit)
library(tmaptools)
library(stplanr)
b = tmaptools::bb("University of Leeds")
p = bb2poly(b)
sp::proj4string(p) = "+init=epsg:4326"
m = mapview(p)
p = editMap(m@map)
plot(p$finished)