Mapio Cartrefi Gwyliau Cymru | Mapping Welsh Holiday Homes

Blog gan Dafydd Elfryn, mapiwr a datblygwr

Scroll down for the translation of this blog post by mapper Dafydd Elfryn

Mae Cymru yng nghanol argyfwng cartrefi. Mae prisiau tai yn cynyddu ar raddfa anhygoel, ac mae cenhedlaeth o bobl ifanc yn gwynebu’r ffaith na allant fyw yn y cymunedau ble cawsant eu geni a magu.

Mae sawl ffactor ynghlwm a hyn, ac un ohonynt yw cartrefi gwyliau. Mewn pentrefi bychain yng Nghymru, mae tai yn cael eu gwerthu am brisiau mawr i bobl o’r tu allan i’r cymunedau.

Er bod y ddadl am gartrefi gwyliau wedi bod yn mynd ‘mlaen ers degawdau, yn ddiweddar, mae’r galw am weithred gan y llywodraeth wedi cynyddu. Mae cyfryngau cymdeithasol wedi gwneud hi’n haws i rannu esiamplau ac i gydgordio protestio.

Fel rhywun sydd yn hoffi creu mapiau, pan fydd trafodaethau fel hyn yn digwydd, mi fyddai’n trio gweld os fedrai greu rhywbeth fydd yn helpu i gyfleu gwybodaeth neu ysgogi trafodaeth. Yn sgil hyn, mi es i ati i drio mapio cartrefi gwyliau Cymru.

Casglu’r Data

Y gamp hefo creu unrhyw fath o waith fel hyn yw casglu’r data craidd at ei gilydd. Mae’n syndod faint o ddata sydd yn cael ei ryddhau gan gyrff cyhoeddus. Mae cyrff fel ONS, Statswales ac Ordnance Survey yn cyhoeddi llwyth o ddata newydd a hanesyddol, ar draws sawl maes. Yr her yw troi’r wybodaeth “amrwd” yma i mewn i rywbeth sydd yn ddealladwy, defnyddiol a diddorol.

Y brif ffynhonnell data ar gyfer y mapiau cartrefi gwyliau ydi’r rhestr trethi annomestig sydd yn cael ei gyhoeddi gan Y Swyddfa Brisio (Valuation Office) – https://voaratinglists.blob.core.windows.net/html/rlidata.htm

Yn fras – mae’r rhestr anferth yma yn cynnwys pob eiddo annomestig yng Nghymru a Lloegr (h.y. eiddo sydd ddim yn talu treth cyngor).

Mae yna dipyn o wybodaeth yma – ac oherwydd maint y ffeil, mae’n waith prosesu popeth. I hwyluso’r broses, y cam cyntaf yw cael gwared ag unrhyw beth da ni ddim angen. Ar gyfer y map yma da ni ond angen cofnodion am gartrefi gwyliau sydd yng Nghymru.

Yn ffodus, mae gan bob math busnes cod gwahanol – ac ar gyfer cartrefi gwyliau, y cod “CH1” sydd yn cael ei ddefnyddio. Mae dileu pob cofnod heb y cod yma yn cael gwared a swm sylweddol o ddata.

I hidlo’r cofnodion sydd y tu allan i Gymru, mi fedrwn ni ddefnyddio’r rhif cod siroedd. Mae gan bob sir yn y DU rhif unigryw (e.e. Gwynedd = 6810, Caerdydd = 6815). Drwy ddileu unrhyw gofnod sydd ddim yn perthyn i siroedd Cymru, da ni’n cael y rhestr derfynol sydd ond yn cynnwys cartrefi gwyliau yng Nghymru.

Mapio’r Data

Di edrych ar restr hir o gartrefi gwyliau ddim yn ddiddorol, ac i drosi’r rhestr i bwyntiau ar fap, rhaid i ni ddefnyddio ffynhonnell data arall. Gan fod pob cofnod yn y rhestr yn cynnwys cod post, gellir defnyddio data agored “Codepoint Open” gan Ordnance Survey i drosi’r rhestr yn ddata daearyddol (https://www.ordnancesurvey.co.uk/business-government/products/code-point-open)

Mae’r data codepoint yma yn rhoi lleoliad canolbwynt pob cod post yn y DU, ac felly drwy gyfuno’r data yma hefo data cartrefi gwyliau – mae modd dangos pwynt ar gyfer pob cartref gwyliau yng Nghymru.

Ar ôl creu’r pwyntiau, mae modd wedyn dadansoddi’r data mewn sawl ffordd wahanol.

Heatmap

Mae’r “Heatmap” isod yn dangos dosbarthiad y cartrefi gwyliau drwy Gymru.

Heatmap yn dangos clystrau o gartrefi gwyliau yng Nghymru (Dafydd Elfryn)

Be sy’n rhyfeddol ydi faint o glir mae’r clystyrau yma yn amlinellu arfordir gorllewinol y wlad. Mae’r ardaloedd hyn yn denu miloedd o ymwelwyr y flwyddyn, ac yn amlwg, yn lleoliadau perffaith ar gyfer cartref gwyliau.

Canran Cartrefi Gwyliau

Mae’r map isod ychydig mwy traddodiadol, ac yn dangos canran yr eiddo ymhob LSOA (‘Lower Layer Super Output Area’ – ardal ddaearyddol fach am ystadegau lleol) sydd yn gartref gwyliau.

Mae’r map uchod yn cadarnhau be da ni’n weld yn y heatmap – mai ardaloedd arfordirol Cymru yw’r ardaloedd mwyaf poblogaidd ar gyfer y cartrefi gwyliau yma.

Er mwyn deall patrymau perchnogaeth yng Nghymru, boed yn dai gwyliau, tir, adnoddau neu asedau, mae mynd ati i greu mapiau dealladwy fel hyn yn rhan bwysig o godi ymwybyddiaeth a chynnau mwy o drafodaethau ynglŷn â phwy bia Cymru, a pham.

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Mapping Welsh Holiday Homes

Wales is in the middle of a housing crisis. House prices are increasing at an astonishing speed, and there is a generation of young people who are having to face the fact that they will not be able to live in the communities in which they were born and bred.

There are many factors that have contributed to this situation, one of them being holiday homes. In small villages in Wales, houses are being sold at inflated prices to people from outside those communities.

Although the debate about holiday homes has been played out for decades, calls for the government to act have increased. Social media has made it easier to share experiences and to coordinate action.

As somebody who enjoys creating maps, when discussion like these occur, I will try and see if I can create something that can help to communicate facts or promote discussion. I decided to try and map the holiday homes of Wales.

Gathering the Data

To create any sort of work like this, you first need to gather the core data. It’s surprising how much data is released by public bodies. Bodies like the ONS, Statswales and Ordnance Survey publish a great deal of new and historical data across many different fields. The challenge is to turn this “raw” data into something accessible, understandable, useful and interesting.

The main source of data for the holiday homes map are the list of non-domestic taxes that are published by the Valuation Office – https://voaratinglists.blob.core.windows.net/html/rlidata.htm

Simply put – this huge list includes all the non-domestic properties in Wales and England (i.e. property that does not pay council tax).

There is a lot of information to process here – and because of the size of the file, it takes time to work through everything. To expediate the process, the first step is to get rid of anything that is not needed. For this map we only need the records for holiday homes in Wales.

Fortunately, each record has a different business code – and for holiday homes, the code “CH1” is used. Eliminating each record without this code gets rid of a significant amount of data.

To filter records from outside Wales, I used the code number for each county. Each county in the UK has a unique number (e.g. Gwynedd = 6810, Cardiff = 6815). By deleting all records that do not relate to Welsh counties, we are left with the final list that only includes the holiday homes in Wales.

Mapping the Data

To look at an extensive list of holiday homes is not interesting in itself, so to translate the list into points on a map, another data source is needed. Since each record in the list includes a post code, it is possible to use the open source data of “Codepoint Open” by the Ordnance Survey to transfer the list into geographical data (https://www.ordnancesurvey.co.uk/business-government/products/code-point-open).

This Codepoint data give the central point location for each post code in the UK, and so, by merging this data with the holiday homes data – it is possible to show a point for each holiday home in Wales.

After creating these points, it is then possible to analyse the data in a number of different ways.

Heatmap

The Heatmap below shows the distribution of holiday homes across Wales.

Heatmap showing clusters of holiday homes in Wales (Dafydd Elfryn)

What is revealing is the way the heat clusters highlight the western coast of the country. These areas attract thousands of visitors annually, and obviously, are perfect locations for a holiday home.

Percentage of Holiday Homes

The map below is slightly more traditional and shows the percentage of properties in each LSOA (Lower Layer Super Output Area – a geographic area for small statistics) which are holiday homes.

The map above confirms what we see in the heatmap – that it is the coastal areas of Wales that are most popular for these holiday homes.

For us to understand more about ownership patterns in Wales, be it holiday homes, land, resources or assets, creating illustrative maps like these will be an important part of raising awareness and inspire more discussions regarding who owns Wales, and why.

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