Data collection with a multi electrode system, such as Lund Imaging System from ABEM, is usually arranged so the dataset is suited for inversion using 2.5D inversion algorithms (Loke and Barker, 1995). This data may not always be suitable for 1D inversion. However, with a 1D inversion approach it is possible to decide the number of layers to be used in inversion and also put in apriori information, where this is available, to lock layer boundaries. This approach is likely to give a result where depths to layers are better determined than with a 2.5D approach. This paper aims to compare inversion with a 2.5D least squares algorithm, Res2Dinv, and the 1D Lateral Constrained Inversion (LCI) algorithm (Auken et al., 2000). The comparison is based on a large dataset collected with a multi electrode system in Lockarp in Southern Sweden (LTH, 2000). There are a large number of geotechnical investigations available, such as auger and core drillings, which can be used as apriori information in the inversions. The geology in the area is sedimentary and consists of Quaternary deposits underlain by Danian limestone. The Quaternary deposits consist of four individually different units. On top there is a half to two meters of high resistive sediments. The second and fourth unit consist of low resistive clay till. In between these two units a third unit consisting up to three meters of high resistive intermorainic sediments can be found in parts of the area. The resistivity data was originally acquired for 2.5D inversion. For LCI inversion the data was divided into individual soundings, one every meter, and all soundings with midpoint within a four meter distance were gathered into one sounding. This results in a dataset with soundings every four meters containing exactly the same amount of data as the original dataset. This means that a sounding might contain more than one data point with the same electrode configuration.


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