IntCal data

The information here covers the data within the IntCal database and is relevant for those using this data or preparing data for possible inclusion in future iterations of the IntCal curve series. There are four key types of data which are included in the IntCal repository. These are:

See also details on preparing data for inclusion.

Record information

The records for IntCal are in the standard format described in the IntChron schema.  The key parameters relevant to the calibration curve are:

Records can be created and edited as normal within IntChron but for dendrochronogical records it is most convenient to create them from the dendrochronologial data  which will provide much of the necessary detail.

Radiocarbon datasets

Radiocarbon datasets included in IntCal have a special format within the IntChron package which is based around the needs of the statistical procedures for curve production.   They are series stored within the record file.

The series should be of series_type "IntCal_Data" which, in addition to the standard series headers has the following:

All of these can be null if the data set is only provisional or being considered for inclusion.

This is followed by the data table, which has parameters which can be broken down into several groups:

Standard IntChron tool parameters

These are used for plotting and other purposes within the database and are common to other types of data series.  Details are given in the IntChron schema but are also described here for convenience:

Special IntCal parameters

The following parameters are important for dataset preparation and interpretation; these are:
The following parameters are used internally in the IntCal curve process and are typically not set on submission of data

Sample naming conventions

The sample (Sample) in the dataset is important.  This should be different for each sample which has a different age - but it should be identical for the same sample measured by different labs.  The labcode should be different for every measurement and is a unique key in the IntCal database.
For dendrochronological samples the sample name should tie up with the dendrochronological series name - suffixed with ring information in the following way.  Supposing the record name is TOW, and the tree sequence name is TOW32A.  The rings within this sequence should be numbered from 1 (the oldest sample) to the last ring.  The radiocarbon sample names will then be like TOW32A_r8 for measurement of a single ring 8 or TOW32A_r1-5 for measurements on a block from ring 1 to 5

Ring numbers and depth information (z, z_range, ring, calage_range)

Most samples come with information either on depth (in a sedimentary sequence, speleothem etc) or ring numbers.  The parameters z and z_range are used to store this information.  At the record level you can define what z is used for (depth, height, rings etc), and this data can be imported/exported and displayed in three different ways:

In the case of tree rings this information is also given in the two columns ring and cal_age_range.  Normally ring and z will be the same but cal_age_range should be 1 for single year rings (like 1 for TOW32A_r8) and 1+z_range for higher numbers (like 5 for TOW32A_r1-5).  Although this arrangement in some ways duplicates information the cal_age_range is directly used in the curve construction and can be checked against the z_range information.  In the case of non-dendro samples z_range is not directly related to cal_age_range.

Dendrochronological data

The most important dendrochronolocal data is the ring-width measurement series for the samples that have been analyzed for radiocarbon.  These should be included within the relevant record for any new submissions but is not always available for historical data.  If the data is available either on the NOAA ITRDB or as a Tuscon format rwl file, the easiest way to import this information is to create the record using the tree ring data because this includes much of the needed information in one place.
Each dendrochronologial sequence has a unique code and ring numbers (z) starting from 1 - these should correspond to the ring numbers in the radiocarbon datasets.  The whole series might be floating (undated) in which case the t values will start from 1 for the oldest ring in the whole series.
In addition to record-based dendrochronological series, it is also possible to store master chronologies as 'Project data' - these are relevant where the radiocarbon dated samples have been dated against a main master chronology for which the details are not provided in the IntCal dataset.


Details on the referencing system are given in the main instructions for the IntChron tool.

Preparing data for inclusion

If you have data which you think might usefully be included in future versions of IntCal you can prepare it for checking, consideration and inclusion using the IntChron tool.  The steps are:

Data preparation

Data compilation

Adding references

Data will not normally be included in IntCal before it has been published in a peer-reviewed journal. The reference information which gives most of the details on the methodology and background for the study should be included in the data submission.  References should be given for each radiocarbon data-set submitted. This can be done by navigating the the relevant data series within the record and adding to the references.  See the general instructions for entering references in the IntChron Integration tool.  References can also be entered for the record where this is appropriate (particularly for dendrochronological series) to give background information on the record.  The radiocarbon data-sets should have references entered specifically for the radiocarbon aspects though even if this repeats records at the record level.
The most straight-forward way of entering publications is using the doi and so where possible have this ready when preparing your dataset.

Checking your data

All of the tools can be used to check that the data is correct.  In particular from the record you can use the [Plot] function to plot the data series and see if this looks correct.  The timescales used for plotting can be set using [Edit > Time] from the top level menu.  You can also check the location information using the [Map] function.

Sending your data

You can share your project with other people, including members of the IntCal committee by downloading the project as a JSON file.  To do this press [File > Download] from the top level menu - include all of the data normally.  The JSON file generated in this way can be stored locally and emailed to colleagues.  They can view the file by going to:

Further details on working with project files is given in the main instructions for the IntChron tool.