01-points.rmd

---
title: "1. Points - Points of points"
output:
  rmarkdown::html_document:
    code_folding: hide
    theme: sandstone   
    highlight: tango
    css: "css/andrewl.css"
    includes:
      before_body: "partials/header.html"
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---
```{r setup, include=FALSE, message=FALSE, warning=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

> Want to see the code? Click on the black boxes on the right to show/hide the code. 

Points. Geographically speaking, a point is a specific location on a map - usually defined
by a pair of co-ordinates. Points are also mechanical switches that enable trains to move from one set of
tracks to another.

![](images/2218837318_1d29a7f419_w.jpg "Points")

So for this map we're going to build a simple map of points (geographical) where you might
find points (railway).

### Data

For this map we're going to take a copy of a dataset provided by National Rail
containing the locations of Timing Point Locations (TIPLOCs).

TIPLOs are places on the railway network used for timetable scheduling. These
might be stations, depots, siding, signals etc, but we can use them as proxies
for places where you might find points.

The data comes as simple Excel file containing the name and coordinates of each
TIPLOC.

```{r data, message=FALSE, warning=FALSE, results='show'}

# Let's load the sf and mapview libraries to process and view geospatial data
library(readxl)
library(sf)
library(mapview)

# We can load the CSV file containing the TIPLOC data straight from the CSV file
# using R's standard read functionality. This will give us a data frame to access
# the TIPLOC data with.

tiplocs <- read_excel('./data/01/TIPLOC_Eastings_and_Northings.xlsx')

# Next we need to convert this to a spatial format. Spatial data has special
# properties - namely coordinates and a spatial (or coordinate) reference 
# system (CRS). A CRS describes the function that's used to map co-ordinates
# on a sphere (the earth) to those on a flat plane (paper or a computer screen).
#
# The TIPLOC csv contains coordinates stored in the EASTING and NORTHING fields
# and these are in the GB Ordnance Survey co-ordinate system - shorthand for this
# is EPSG:27700 or 27700
tiplocSpatial <- st_as_sf(tiplocs, coords = c("EASTING", "NORTHING"), 
                                   crs = 27700)

```

### The Map

And here we have it - a map with points where you might find some points!
```{r map, results='show'}
# Here we use mapview to display the map using the leaflet library.
# Because tiplocSpatial is an sf object rather than a plain datatable
# leaflet understands how to interpret the coordinates and reference system
# to display the points in the correct location on the map.
mapviewOptions(basemaps = c("Esri.WorldShadedRelief"),
               layers.control.pos = "topright",
               leafletWidth = "100%",
               legend = FALSE
               )
mapview(tiplocSpatial, label="NAME")
```


### Credits

Data: _TIPLOC data from National Rail licensed under OGL3, sourced from https://wiki.openraildata.com/index.php/Identifying_Locations_

Image: _"Dockland Light railway points and crossing01" by Elsie esq. is licensed under CC BY 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/2.0/?ref=openverse._