This image shows the Maqueda barrio in Malaga, with streets colour-coded by estimated gradient. The flat area to the east shows up with cold colours, while the western part of the barrio, which straddles a ridge, generally has warmer colours. But why did I make this map, and what does it have to do with “streets that are really steps”?

In my wanderings around the city of Malaga, I have often come across flights of steps that are not tagged as highway=steps in OpenStreetMap. Usually they are tagged as residential or footway, with misleading results for anyone using OSM-based maps or routers to find their way around the city.

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Recently Malaga’s bus route number 37 was extended to Residencia Santa Clara in the hills outside the city. This part of the route had been suspended for a few years, and I knew that some stops had been relocated in the meantime. So I took the bus to the last stop to update the mapping in OpenStreetMap.

As I walked back towards the city down a steeply sloping road (pausing to tag it as sidewalk=no), I wondered if I had just visited the city’s highest bus stop. I could probably have confirmed this fairly quickly with the help of a relief map - there were only a few realistic candidates.

But I happened to be looking at the OSMnx Python package for unrelated reasons. And I had already downloaded Digital Terrain Model files covering the city of Malaga. Obviously destiny wanted me to take a library intended for analysing important questions about urban road networks, and use it to devise an over-engineered answer to my trivial question about bus stops.

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In Part 3 I talked about changes in POI data in a small area over a period of two months. Most of those changes were due to mapping activity, rather than anything that happened in the real world over that period. But I’d like to use a similar approach to better understand how the real-world POIs are evolving.

As I mentioned in Part 3, until recently a significant proportion of POIs in this area had never been mapped in OSM. That means there is no point in the past at which OSM data is anywhere close to a complete set of POIs for this area. But we might be able to learn something from the POIs that were mapped some time ago.

I chose to look back 5 years, to August 2019. I guessed that was roughly the point at which the data was most accurate. Most POIs were added in 2017-2018, so while lots of POIs were missing, those existing in 2019 were probably still fairly accurate. This is how those specific POIs evolved over 5 years, ignoring anything newly created over that period:

	POI count	as %
no major change	135	57%
removed	42	18%
changed POI type	38	16%
changed name	22	9%
total	237	100%

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As I mentioned in Parts 1 and 2, over the last couple of months I set out to systematically update Points of Interest in four adjoining barrios in the city of Málaga.

A few businesses really did open, close, or change hands over that short period. But the vast majority of the changes in the data reflect the OSM data “catching up” with reality: adding points that had never been mapped in OSM, or updating POIs that had changed in some way since they were last touched by an OSM mapper.

Adding leisure POIs

Closely examining changes over a period is a good way of revealing faulty assumptions. I noticed that three shop locations had disappeared from my data, even though I was sure there were still businesses at those addresses. They are all gyms now, and gyms are tagged as “leisure” - a tag I had completely ignored. I’ve now added leisure POIs. As with “amenity” tags, I excluded some high-volume tags such as “garden” and “swimming pool”. I now have 392 POIs in my current dataset, not 376 as I mentioned in previous diary entries.

Changes over the period

	POI count	count distinct feature tags
mid Aug 2024	267	96
+ newly created	141	34
- removed	(16)	(9)
late Oct 2024	392	121
% change	+47%	+26%

I mentioned in a previous post that I thought that POIs were reasonably well mapped in this neighbourhood. The numbers suggest that about two thirds of POIs were mapped two months ago. That seems respectable, but not great. There has not been any major expansion of retail space in this area recently. Some of the new additions are locations that were vacant or derelict when the area was first mapped in detail, but the majority have existed for a long time and were simply never mapped in OSM.

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Brands

As part of my systematic update of local POIs (see Part 1), I added the “brand” and “brand:wikidata” tags wherever I could identify them. Before I started I thought I might find quite a few POIs that I had not previously recognised as brands.

Spoiler: I was wrong, yet again. It’s good to have your preconceptions challenged by actual data. I guess.

It turned out that the reason I hadn’t heard of most of the brands displayed on POIs in this area, and the reason not many POIs had the brand tag before I started mapping, was that … they aren’t brands. It’s possible there are a few shops belonging to brands so obscure or localised that I couldn’t find any reference to them online, but I don’t think I can have missed many.

Out of 376 POIs, only 36 - less than 10 percent - are now tagged as brands.

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Recently I have been trying to systematically improve OSM data about shops, businesses, and other Points of Interest in a small area of my city. Like many OSM contributors before me, I have been torn between the desire to make my local map as complete as possible, and the realisation of just how much time is needed to do that. My observations in the following series of diary posts may not be very original, but perhaps they’ll help me to clarify my thoughts on the subject.

Background

Málaga is divided into about 200 barrios or neighborhoods, all with well-defined boundaries in OSM. I chose to focus on an area of four adjoining barrios slightly to the northeast of the historic centre. The main axis of this area, formed by Calle Victoria and Calle Cristo de la Epidemia, is about 1km long (the green dashes in the map below). These main thoroughfares, and many of the smaller streets, are lined by apartment blocks with commercial premises on the ground floor. The hillier areas to the east are more purely residential. Most shops are quite small, many are sole traders, and there are no shopping malls.

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