A system, comprising: an implantable stimulator device (10; 110; 50; 150), comprising: a plurality of electrode nodes , each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes , and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes ; and an external device (60; 70) configured to communicate with the implantable stimulator device (10; 110; 50; 150), the external device (60; 70) comprising: second control circuitry (66; 88) configured to render a graphical user interface , wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm , receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient. an implantable stimulator device (10; 110; 50; 150), comprising: a plurality of electrode nodes , each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes , and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes ; and a plurality of electrode nodes , each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes , and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes ; and an external device (60; 70) configured to communicate with the implantable stimulator device (10; 110; 50; 150), the external device (60; 70) comprising: second control circuitry (66; 88) configured to render a graphical user interface , wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm , receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient. render a graphical user interface , wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm , receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient. <EOS>