ROpenLayers: ROpenLayers: A pacakge for Geo-Visualization

In cemarks/ROpenLayers: Geo-visualization Using OperLayers and ArcGIS

ROpenLayers: A pacakge for Geo-Visualization

Description

ROpenLayers leverages the power of OpenLayers javascript libraries and web-based Mapservers to enable informative visualization.

What this package does

The purpose of this package is to make it easy for a user to visualize geo-spatial data and analyses using the open source OpenLayers javascript library and online map servers. The process for creating a visualization imitates the process of creating a plot in R package ggplot2.

1. First, an OpenLayers Map object is created with a call to the ol_map method.

2. Next, layers and scales are created and added. Layers can reference map servers to provide underlying base maps or vector features (polygons, lines, or points) created or imported in R. These capabilities are described in the following sections.

3. Finally, the updated map object is exported to HTML/javascript for viewing in a browser, hosting on a server, or embedding into another application or format. Export methods are ol_map2HTML and ol_map2Strings.

OpenLayers

OpenLayers is an open source javascript library that makes it easy to put a dynamic map on any web page. It is licensed under the 2-clause BSD license (see OpenLayers Licence). This license will appear commented within OpenLayers CSS code in the HTML exports created by this package. However, this package does not contain any of the OpenLayers javascript source code; rather, it exports HTML code that source these libraries when loaded. Therefore, these products will not render without network access to the OpenLayers javascript library. By default, the products exported by this package source OpenLayers 3.16.0, but the user has the option to set the source URL (see ol_map).

Public ArcGIS Servers

ESRI ArcGIS hosts several publicly available map servers at arcgisonline.com, which can accessed via REST APIs and rendered using OpenLayers javascript methods. A subset of these are made available in this package through the public_arcgis_basemap method. Alternatively, a user can specify any ArcGIS map server using the user_arcgis_basemap method. Note that while these maps servers are publicly available, they are not necessarily open-licensed. Users must ensure they comply with each map server's license and terms of use.

OpenStreetMap

OpenStreetMap also hosts a public and open license map server that can be imported as a layer using OpenLayers. See public_OSM_basemap.

Other Servers

As stated above, the user_arcgis_basemap method allows the user to manually specify any available ArcGIS map server. This package also provides access to US National Geospatial-Intelligence Agency servers hosted at NGA.mil through the nga_basemap method. Note that these servers require authentication, which will be requested at the time of access (i.e., when the HTML page is opened in a browser).

Vector Layers

This package enables users to rapidly access and write OpenLayers vector layers in javascript. The following methods enable that functionality.

• ol_geom_polygon

• ol_geom_line

• ol_geom_point

• ol_geom_icon

• ol_geom_circle

• ol_geom_heatmap

• ol_geom_text

Geocode

New in version 1.0.0–geocode addresses using ArcGIS geocoding service. See geocode.

Examples

data(quakes)
center <- c(mean(quakes$long),mean(quakes$lat))
quakes$long[which(quakes$long>180)]<-quakes$long[which(quakes$long>180)]-360
tooltips <- paste("Depth",quakes$depth,sep=": ")
mymap <- ol_map(
    zoom = 5,
    center = center
)
basemap.layer <- oceanbase()
point.layer <- ol_geom_point(
    quakes[,c("long","lat")],
    mapping = ol_aes(fill=mag),
    df = quakes,
    name = "Earthquake Points",
    toggle.control=TRUE,
    tooltip = tooltips
)
heatmap.layer <- ol_geom_heatmap(
    quakes[,c("long","lat")],
    name = "Earthquake Heatmap",
    toggle.control=TRUE,
    weight.values = quakes$mag,
    opacity = 0.25
)
mymap <- mymap +
    basemap.layer +
    point.layer +
    ol_scale_fill_continuous(name="Magnitude",display=TRUE) +
    heatmap.layer
## Not run: 
# Save to file and open in browser
ol_map2HTML(
  mymap,
  "Quakes.html",
  map.heading = "Earthquake Data Visualization"
)
browseURL("Quakes.html")

## End(Not run)

cemarks/ROpenLayers documentation built on March 31, 2022, 12:05 p.m.