Vector Tiles Part 1 - Creation

Vector Tiles Part 1 - Creation

Vector tiles contain vector representations of data across a range of scales. Unlike raster tiles, they can adapt to the resolution of their display device and even be restyled for multiple uses. With ArcGIS Pro 1.4 users can now also publish their data as vector tiles using local projections such as British National Grid. In this first of two posts, I'll take you through the steps required to publish your own vector tiles using a local projection.

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The science behind our Coastal Views map

The science behind our Coastal Views map

When you're at the coast and gaze off into the horizon, do you know which countries are directly across the sea from you? I recently tried to answer this question by creating a map that went on to be featured on The Telegraph, Mail Online, BBC News and, more recently, Esri's Maps We Love gallery. 

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US election 2016: battle of the maps

As America prepares to elect its 45th president, many media agencies are opting to use cartograms instead of traditional maps. Want to know why? As well as looking at the general benifts of using cartograms I've also looked at the strengths and weaknesses of different types.

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Items and time in the summer update to ArcGIS Online

The summer's update to ArcGIS Online went live at the end of last week. It brings us a mixture of new capabilities and further refinements to the content management and administration functions. In this post I'm taking a look at two key changes - the new Item page and time options in Smart Mapping. Remember to check the what's new page for a full list.

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New OS Open Basemaps available for free in ArcGIS Online

With the latest release of ArcGIS Online you now automatically get access to free high quality basemaps for Great Britain. We have created the new basemaps using the latest Ordnance Survey Open Data products and enhanced them for use in the ArcGIS platform. Enhancements include a consistent cartographic style to provide a clean and consistent mapping from small to large scale, as well as additional road and street labels at mid and large scales.

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Coordinate systems and projections for beginners

This blog post gives a basic introduction to coordinate systems and projections, with a focus on UK data. To seasoned geographers, I apologise for all the things I've simplified or simply left out! My intention is to provide GIS novices who are a bit confused by the topic with just enough about various different coordinate systems to get started working with them in ArcGIS. Anyone looking for an excellent comprehensive introduction should refer to Ordnance Survey's guide.

A coordinate system lets us define where a location is in space. In GIS, there are many types of coordinate systems, of which the two most used are geographic (3D) and projected (2D). The difference is shown below:

A geographic coordinate system (GCS) uses a grid on the surface of a 3D globe (the technical term for this grid is graticule; the North/South lines are lines of longitude and the East/West lines are lines of latitude). Graticule lines are not parallel to each other because they are defined using angles (e.g. degrees) from the centre of the globe, not linear units (e.g. metres) on a flat surface.

A projected coordinate system (PCS) is a flattened version of a 3D coordinate system. Grid lines are parallel, and coordinates are given in "flat" units like metres or feet. Although the Earth isn't flat, we often use flat surfaces to represent it (paper surfaces, computer screens, etc), so we frequently need to convert 3D coordinates to 2D coordinates. However, there's a problem: imagine peeling the skin off an orange and trying to make it sit flat on a table. It's not possible to do this without ripping or stretching the peel! It's the same with a 3D coordinate system. Whenever we flatten, or "project", a 3D coordinate grid to a 2D coordinate grid, we have to distort the grid's proportions somehow. Distances, shapes, areas, and angles, or some combination of all four, are deformed.

If you work with UK data, there are two geographic and two projected coordinate systems that you should know about. They are shown in the diagram below, along with the numeric WKID (Well-Known ID) of that GCS/PCS, as well as their relationships with one another and example coordinates in each system showing the location of Esri UK's head office in Aylesbury.

World Geodetic System (WGS-84) is familiar to many non-geographers because it is used by GPS devices to describe locations all over the Earth. A different GCS, called OSGB-36, which is more accurate for describing locations in Britain but not as good for other countries, is used specifically for British data. Web Mercator is a PCS based on WGS-84 used for global maps, and British National Grid is a PCS based on OSGB-36 used for British maps.

For each GCS, there are many different ways of converting, or "projecting", 3D coordinates to 2D coordinates. Web Mercator and British National Grid are the most important projections for their respective geographic coordinate systems. There are alternative projections, each with its own pros and cons (this link has more information, as well as an entertaining video clip).

Converting between coordinate systems that are based on the same GCS is relatively straightforward, but when converting, for example, GPS (WGS-84) coordinates to BNG eastings and northings, a mathematical transformation is required. The "Petroleum" transformation is an accurate transformation from WGS-84 to OSGB-36 (and vice-versa) included with ArcGIS.

To convert data between WGS-84 and BNG in ArcGIS Desktop, you should use the Project tool. Make sure you select the "Petroleum" transformation otherwise your results will not be accurate.

Select the optional Petroleum transformation for the best results

For GB data, you only really need to know about WGS-84 and BNG, and that you should use the Petroleum transformation to get an accurate conversion between them. You will also need to use "Petroleum" to convert between BNG/OSGB-36 and Web Mercator (or WGS 1984 Web Mercator Auxiliary Sphere, to give it the name used by Esri). Web Mercator has become the standard projection for international consumer web maps, such as Google Maps, Bing Maps, and OpenStreetMap. All ArcGIS Online basemaps are also in this projection.

Considering colour vision deficiency when designing maps

A few months ago I was given the opportunity to visit a client to discuss cartography and how they can communicate spatial information in an efficient and effective manner.

Whilst preparing for the visit, I started to investigate Colour Vision Deficiency (CVD) and came across some interesting facts, tools and techniques which I’d not really considered enough before.

Whilst there are a number of different types of Colour Vision Deficiency, the most common is ‘red-green blindness’ which affects approximately 8% of males (Jenny and Kelso, 2007). Of this impairment, the most prevalent type is Deuteranopia. Whilst this might not seem a large percentage, this group of users should not be disregarded when designing maps.

One of the most useful tools I discovered is Color Oracle which can be found here: http://colororacle.org/. This is a free little utility which simulates CVD on screen and it’s quickly become an invaluable tool when I design and create maps.

One thing I hadn’t realised is how hard it is to distinguish the subtleties of the commonly used red to green colour ramp for people with colour vision impairments. This colour scheme gets used a lot, especially in hotspot mapping. I personally used this colour scheme since I felt it represented something effectively on a scale of low to high, or ‘good’ to ‘bad’. Since we’re all used to the traffic light system it’s such a common way to represent a range of data. But how is this seen by someone with CVD?

Figure 1 shows how someone with “normal” vision would view a map of wind speeds around the UK. The red areas represent higher wind speeds and the green areas represent lower speeds. But now, consider how this same data might viewed if you suffer from Deuteranopia (the screenshot is simulated using the Color Oracle utility). This clearly shows how hard it is to determine which areas of the UK have high and low wind speeds.

Figure 1. The left map illustrates normal colour vision and the right simulated Deuteranopia (Red-green blindness). Both maps use a red to green colour scheme. Data shows mean UK wind speed from DECC.

So what are the alternatives to displaying such data? Well, there are a number of different strategies and as always it depends on the data and the message that you’re trying to communicate. However one simple option is to change the colour scheme to a red to blue diverging ramp (in ArcGIS Desktop this is called ‘Cold to Hot Diverging’). The advantage of using this is that red can still represent high wind speeds in this example whereas lower speeds are now represented as blue instead of green. Figure 2 shows how this data would appear with normal vision shown against how this compares with some who has Deuternanopia. Both maps are now legible and the high and low wind speeds are distinguishable.

 

 Figure 2. The left map illustrates normal colour vision and the right simulated Deuteranopia (Red-green blindness). Both maps use a red to blue colour scheme. Data shows mean UK wind speed from DECC.

There are a couple of other excellent resources which I would highly recommend looking at. Firstly, for a more thorough discussion of designing maps considering CVD then “Designing maps for the colour-vision impaired” by Bernhard Jenny and Nathaniel Vaughn Kelso is a fascinating read. It’s full of theory and practical advice. A .pdf of the paper can be found here.

Also, for designing colour schemes for choropleth maps, ColorBrewer is an excellent resource. It allows you to select qualitative, quantitative and sequential colour schemes and also has an option for suggesting schemes which are CVD safe. ColorBrewer can be found here and again, I find it extremely useful.

Finally, there is a more general blog article from the Esri Mapping Centre which highlights some excellent colour tools for map makers which can be found here. Also, there is a set of styles designed for maps for the colour deficient in the ArcGIS Resources section.

It is clearly important to carefully consider the colour schemes that you’re using when creating maps. This will help ensure that the information that you’re presenting is meaningful to the widest possible audience. As mentioned earlier, I now use these tools and techniques whenever I’m creating maps and I frequently check symbology using the Color Oracle tool. It’s become an invaluable part of my workflow.

 

Reference:

Jenny, B. and Kelso, N.V. (2007). Designing maps for the colour-vision impaired. Bulletin of the Society of Cartographers SoC, 41, p. 9-12.

Using ArcGIS Desktop and Adobe Illustrator to create a poster mapping Solar Potential.

If you've recently visited our Office HQ in Aylesbury you may well have noticed a poster proudly displayed in the foyer showing Solar Potential Mapping. I've been producing a number of posters showcasing work that Esri UK are undertaking and this is one example. The poster explains how GIS can be used to model Solar Potential as part of some of the Low Carbon work being carried out by Esri UK. This blog article will briefly describe how this poster was created and the main tools which I used.  

Please click map for a higher resolution (2.2mb) version in a new window.

The Geoprocessing tools in ArcGIS Desktop were used to undertake all of the necessary calculations and create each layer used within the map. These were then combined with ModelBuilder to process the data for an area surrounding Oxford City Centre, an area which many people are familiar with. The cartography in the main map was produced using a combination of standard ArcGIS Desktop tools, Maplex for ArcGIS, Cartographic Representations and some of the more advanced Cartography tools to perform processes such as simplifying the road system. This combination of tools allowed me to create a very pleasing cartographic output. Each map inset in "The Process" box was also created as separate layer in ArcGIS and exported as individual images. 

For this poster I was keen not only show the interesting mapping outputs generated from calculating solar potential, but also to explain the broad process behind how to create these outputs. I hand sketched numerous layouts before deciding upon the one presented in the final poster. The layout of this poster, in particular the complexity I wanted to use in the process section, helped with my decision to use Adobe Illustrator for the final poster production.

All of the insets, logo's, titles, drop shadows, arrows, and text placement were carried out in Illustrator.

 

The process flowchart/diagram was also constructed in Abobe Illustrator. I was particularly keen that the round insets maps acted as "magnifying glasses" through to the appropriate layer of interest. This visually represents the power of a GIS being able to peel away layers of information to reveal more interesting data! All of the map layers and cartography for these were produced in ArcGIS and exported as TIFF images and then all placed in Illustrator. I used the greyscale duration layer as a basemap to add context mainly because I thought the output was so visually interesting! The geography of each "magnifying glass" matches the geography on the underneath. 

There are various different options for interoperating mapping between ArcGIS and Illustrator. For the purpose of this poster though I exported the maps out as high resolution images and then placed them into an Illustrator document. I decided to use this method mainly due to simplicity and I didn't want to modify any of the cartography within Illustrator. However, it is possible to export to Adobe .ai format from ArcGIS which is another option for working between the two applications. This will give you more control over the exported features so you can modify the elements in Illustrator rather than exporting just an image. If you decide to export from ArcGIS to .ai then there are a number of issues to be aware when creating your Map Documents (MXD's) prior to exporting. These include not using transparency in your layers and also not nesting your layers in the Table of Contents. 

As ever, the Esri Mapping Centre has a wealth of information and tips for working with cartography in ArcGIS. There are also some Illustrator specific articles which can be found here
In a future post I will consider some more specific tips and tricks of exporting content from ArcGIS to Adobe Illustrator. If you have any suggestions for future blog topics of a cartographic nature or if you have any further questions or comments about the Solar Potential Mapping poster then I would be delighted to hear them.

 

More information on the Low Carbon work at Esri UK can be found
at http://www.esriuk.com/industries/lowcarbon and the Solar Radiation Geoprocessing tools here.

Tip for working with many colour ramps in ArcMap

I have recently started using some of the Colour Ramps available at the Esri Mapping Centre which are great for symbolising a variety of continuous surfaces and build on the out of the box ramps provided in ArcGIS. The downloadable colour ramps (from here) have many many to choose from so when you load the styles into ArcGIS Desktop it is quite hard to keep track of them and see which colour ramp is which.

For example it is hard to distinguish between the following elevation colour ramps:

 However, if you right-click on the Color Ramp drop down you can un-check “Graphic View”.

When you look at the colour ramp drop down now you can see the name of the colour ramp. You can then more easily choose your colour ramp.

A useful tip when you have many colour ramps for specific needs, or perhaps if you suffer from colour blindness!

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