HistData (version 0.8-6)

OldMaps: Latitudes and Longitudes of 39 Points in 11 Old Maps

Description

The data set is concerned with the problem of aligning the coordinates of points read from old maps (1688 - 1818) of the Great Lakes area. 39 easily identifiable points were selected in the Great Lakes area, and their (lat, long) coordinates were recorded using a grid overlaid on each of 11 old maps, and using linear interpolation.

It was conjectured that maps might be systematically in error in five key ways: (a) constant error in latitude; (b)constant error in longitude; (c) proportional error in latitude; (d)proportional error in longitude; (e) angular error from a non-zero difference between true North and the map's North.

One challenge from these data is to produce useful analyses and graphical displays that relate to these characteristics or to other aspects of the data.

Usage

data(OldMaps)

Format

A data frame with 468 observations on the following 6 variables, giving the latitude and longitude of 39 points recorded from 12 sources (Actual + 11 maps).

point

a numeric vector

col

Column in the table a numeric vector

name

Name of the map maker, using Actual for the true coordinates of the points. A factor with levels Actual Arrowsmith Belin Cary Coronelli D'Anville} \code{Del'Isle Lattre Melish Mitchell Popple

year

Year of the map

lat

Latitude

long

Longitude

Details

Some of the latitude and longitude values are inexplicably negative. It is probable that this is an error in type settting, because the table footnote says "* denotes that interpolation accuracy is not good," yet no "*"s appear in the body of the table.

Examples

# NOT RUN {
data(OldMaps)
## maybe str(OldMaps) ; plot(OldMaps) ...

with(OldMaps, plot(abs(long),abs(lat), pch=col, col=colors()[point]))
# }