HTML Geo Tag Informator (2/2)
Learn more about the Format of HTML Geo-Tags:
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Format of HTML Geo-Tags
Common characteristics of all geo-tags are:
- Geo-tags are located inside the head section
</head>) of the html page.
- Geo-tags are so called html meta-tags and therefore start with the keyword "meta".
- As many meta-tags, geo-tags base on a syntax consisting of name (name="...") and content (content="...")
- For Xhtml conformity it is essential, to complete each meta-tag with a closing slash and to use small letters for identifier (meta, name und content). Both are not necessary when using simple html.
<meta name="geo.position" content="48.169822;11.601171" />
In its content field the geo.position tag contains first the geographic latitude and arranged behind the geographic longitude. The separator between both values obligatory is a semicolon (;). The decimal separator has to be a period (.) and not a comma. The values are expressed in normal decimal notation and not as angular degree, minute and second - they depend on the WGS-84 coordinate system (World Geodetic System 1984). Latitudes south of the equator have to be noted with a leading minus sign (-), as well as longitudes west of Greenwich. A leading plus sign "+" for latitudes in the northern hemisphere or longitudes east of the prime meridian is syntactically correct but unusual.
The number of used digits behind the decimal point is free to the user. So - if desired - you can reduce the accuracy of the geo.position item to protect your privacy by stripping digits from the right side of latitude and longitude. Assistance on this is provided by the Geo-Tag-Generator.
Optional is an altitude value (in meters) - separated from the longitude by a second semicolon. Only write the value without the "m" for meter. However up to now, a height statement is rather uncommon.
<meta name="geo.region" content="DE-BY" />
The geo.region tag is composed of two parts: country code and regional code. Separator between both is a hyphen "-" (also permitted but quite unusual is an underscore character "_"). Additional spaces in front or behind the hyphen are not allowed. The regional code is optional for countries that don't have regional codes. But if the regional code drops, also the hyphen has to be omitted, in this case only the single country code remains.
Country codes always consist of two capital letters, corresponding ISO-standard "ISO 3166-1". For example "GB" for Great Britain, "US" for the United States or "AT" for Austria.
Regional codes consist of 1 to 3 capital letters or numeric characters, corresponding ISO-standard "ISO 3166-2", such as "GLS" for Gloucestershire (GB), "CA" for California (US) or "7" for Tirol (AT).
Not normative - even if often seen so - is to use a full word region instead of an unknown regional code like "DE-Bayern" for example. The only correct version would be "DE-BY".
<meta name="geo.placename" content="München" />
The geo.placename tag - as the word suggests - is nothing else than the name of the place. Typically the place is your city or the nearest town. Avoid here specifications that are already components of the geo.region tag such as country or region name. They need not be mentioned twice. On the other hand, you should include detailed specifications especially if there is more than one city with identical name such as "Garching an der Alz" and "Garching bei München". Take care to use a common geographical place name and not a personal description such as "Place of my homepage" or the name of a company.
Using national special characters, like the German umlauts "Ä Ö Ü" for example, you should consider that you have to code your place name with the same character set (ISO-8859-1, UTF-8) you specified in your html header or you replace them with their html equivalents (Ä Ö Ü).
Related HTML Tags
The following html meta-tags are no geo-tags, but they are often used in connection with them. Therefore they will be created by the Geo-Tag-Generator and inspected by the Geo-Tag-Validator. Absence of these tags however has no impact on the validity of your geo-tags.
<meta name="ICBM" content="48.169822, 11.601171" />
The ICBM tag (for: intercontinental ballistic missile) is a prior existing equivalent to the geo.position identifier and therefore widely-used. The notation is similar to geo.position tag, with one difference: the separator between latitude and longitude is not a semicolon but a comma. If both tags (ICBM and geo.position) are used - what absolutely makes sense - the coordinates should correspond of course.
<meta name="DC.title" content="Geo Tag Validator" />
The DC.title tag is in no way concerned with geo referencing. It is one out of the "Dublin Core Meta Tag" family and correlates with the common title tag. It is merely mentioned here because some geo databases extract the web-page's title out of the DC.title tag. Just set the DC.title corresponding to your ordinary title statement.
Read more about the meaning and purpose of geo-tags ...